LIBRARY OF THE UNIVERSITY OF CALIFORNIA. GIPT MISS ROSE WHITING. Deceived September, i8g6. Accession No.#J} y*J0 3- Class No. i A POPULAK TREATISE 0^ GEMS <5^ ^ 7^4 / X? A POPULAR TREATISE ON GEMS, IN REFERENCE TO THEIR SCIENTIFIC VALUE: A GUIDE FOR THE TEACHER OF NATURAL SCIENCES THE LAPIDARY, JEWELLER, AND AMATEUR: TOGETHER WITH A DESCRIPTION OF THE ELEMENTS OF MINERALOGY, AND ALI ORNAMENTAL AND ARCHITECTURAL MATERIALS. BY DK. L. FEUCHTWANGEK, H AND MINERALOGIST, MEMBER OF THE NEW YORK LYCEUM 0V AT. HIST., AMERICAN ASSOO. OF SCIENCE, OF THE MINEBALOGICAL SOCIETIES OF JENA, ALTBNBURG, ETC. THIRD EDITION. NEW YOEK: PUBLISHED BY THE AUTHOR, No. 55 CEDAB ST. 1867. Entered according to Act of Congress, in the year 1S69. BY DK. L. FEUCIITW^NGEE, In th* Clerk's Office of the District Court of the United States for the Southern District of New York. JOHN W. AMEBMAN, PRINTKK, No. 4T Cedar St., N. Y. PREFACE IN none of the numerous works on Mineralogy that have lately been published, have GEMS been treated in a manner commensurate with the important rank which they hold in the mineral kingdom. The author of this treatise published in 1838 a small work on Gems, which was well received by the scientific world. As that edition was soon disposed of, the author intended to issue a larger and improved edition, but close application to his legitimate pursuits prevented him from accomplishing that object. In 1851 he visited the London Exhibition, where the treasures of the mineral kingdom, and the profusion of brilliant and costly gems from all quarters of the globe, formed a collection such as had never before been wit- nessed ; and he then resolved to embody the facts which he had there collected in a ne\v work on Gems, which he has been encouraged to publish by the solicitations of numerous teachers and jewellers, who had used his former treatise as a work of reference, and who wish to have a work that will impart useful and correct information in regard to tjie locality and value of Gems in the present state of scientific knowledge. As a work on Gems would be incomplete without a treatise on Mineralogy, and as the author did not wish to enter into details foreign to his subject, he was at a loss how to commence ; but on consult- ing the recent works on the Elements of Mineralogy of Pro Nichols and Zimmerman, he was conviiu:< <1 that a summary PREFACE. of the leading principles of Mineralogy was indispensable, as ar introduction to his main design ; and that Crystallography, the mother of Gems, should be explained, before treating them when prepared for the dealer or wearer : he concluded, therefore, to commence his treatise by following the Terminology of Nichols' Elements of Mineralogy, of which he copied the greater part, along with some remarks of Dufresnoy, from the study of whose great work on Mineralogy he derived much valuable informa- tion. He feels it incumbent on him publicly to acknowledge his obligations to the author of the Elements of Mineralogy, for the concise and lucid descriptions contained in the first part of that work, which should be read by every student of Mineralogy. In the second part of this work, which treats of Gems, the author has followed his own system in their classifi- cation j that is, he has arranged them according to their in- trinsic value, and not alphabetically, as has been done by some authors, nor as oxydized stones a system adopted by others. The diamond is placed at the head of the whole class of Gems, and the others follow in the order of their commercial value. Some minerals which are not properly Gems have been in- cluded in the list, either on account of certain specific characters which they possess, or their applicability to some useful purpose. Many mineral substances which belong properly to the geolog- ical or economical department of the science of mineralogy, have been treated in this part of the work ; but they occupy so important a position in the economy of life, that their intro- duction cannot be regarded as an intrusion. Reference is here made to the detailed account of coal, marble, granite, and sienite are they not as valuable as the Gems described in this treatise ? are they not the foundation on which is to be reared the opulence of future generations? have they not already contributed to the aggrandisement of the United States, the most enterprising nation on the globe ? The revenue arising from he annual production of eight PREFACE. 7 million tons of coal is not inconsiderable. The marble of the country, which is just beginning to be developed, bids- fair to compete with that of any other country, .and to revolutionize the civilized world. The marble from California, that from the quarry lately discovered in Pennsylvania, the Leocadia Breccia, the Verde- Antique of Vermont, and the white marble from Canaan, Conn., which is used in the construction of the Fifth Avenue Hotel, Madison Square, N. Y.,*are referred to as illustrations. Are not the sienites and the granites which have, been quarried for the last fifty years; and which have been used in the erection of all our public edifices, really as valuable as Gems ? Few persons were aware, until recently, of the existence of fancy (variegated) marbles in this country ; and Italy, Greece, and Ireland furnish the materials for ornamenting fine houses and cemeteries, because our own resources have been overlooked, or not developed. What will be the condition of things fifty years hence, when the fine arts will occupy as prominent a po- sition in this country as in any other, and when wealth and taste will compete with the arts and sciences for the ascendency ? The Almighty has converted the vegetables of the forest into a mineral substance, the animals of the sea into building-stone, and endowed man with the faculty of exploring and developing the hidden treasures of nature, and this faculty will soon render this country independent of all other nations. The principal aim .of the author has been to explain not only the useful, but also the ornamental mineral substances, and such compositions called mosaics as are prepared from them, and he is indebted for much valuable information pertaining to this branch of the t subject to the Jury Report of the London Exhibition. PEEFACE TO THE THIED EDITION. THE publication of 1859 having been exhausted for several years, the numerous applications from booksellers for a supply have in- duced the author to issue another edition, and to improve it in add- ing an Appendix to the work on such subjects which, in his judg- ment, was considered indispensable ; it was to give to his readers the chronology of mineralogical knowledge, from its first dawn to the present day, and with much perseverance and labor he accom- plished this task. It was thought advisable and useful to add tables of the distinguishing characteristics of gems, so as to have at one glance a condensed survey of the physical and chemical characters of all the gems, and they were, therefore, copied from Mr. Harry Emanuel's late work on Diamonds and Precious Stones, as also many remarks on the value and market prices of gems, etc. The author was requested to have his likeness placed in front of the work, and reluctantly complied with it ; but while doing so, he is satisfied that his numerous friends on the Pacific will consider it acceptable. On account of the latter change, the former frontispiece had neeessarily to be altered, and the best place was Part III., where the individual gems were treated on page 183, but the Kohinoor and Zircon crystals were deemed best to be replaced by other gems, which his friend, Mr. G. CX Newcomb, kindly furnished him for copy- ing ; they are a large Ruby spinelle of 100 carats weight, and a large Hyacinthe, and a beautiful precious Opal, which were photo- graphed along with various gems and executed very faithfully. In the present great Paris Exposition, according to the official catalogue, a great many valuable gems are mentioned, such as the Crown Jewels of France ; those from the Queen of Sweden ; also those of Russia ; and from the various English, German, Turkish and French jewellers ; also, a Brazilian Topaz, of 3 Ibs. weight, 7 inches long and 4f inches wide, has recently been deposited. The extensive display of Corals, one set of which was valued at $2,300, and many others, but, for want of a detailed description, could not be enumerated in this Treatise. The author had latterly occasion to examine at the jewelry store of Messrs. Bishop & Rein, under the Fifth Avenue Hotel, New- York, a beautiful white Brilliant, of 14 carats weight, and a great variety of splendid pink Corals. Also, at Doucet's store, Montreal, from Thunder Bay, Lake Superior, large masses of Amethysts, weighing several hundred pounds. The author takes pleasure in recommending the Heliographic Engraving Company, under the superintendence of Baron Egloff- stein.; the author's likeness having been executed by them with much skill. Praise is also due to Mr. Schnapauff, who much improved the oojoring of the gems, many of them true to nature. With these few remarks, the author commits herewith the present edition to the reader, and trusts it may prove useful and instructive, which will ever gratify the public servant, LEWIS FEUCHTWANGER, M. D. NEW-YORK, June 1, 1867. CONTENTS. PAG* INTRODUCTION 13 PAET I. TERMINOLOGY. CHAPTER I. Form of minerals 19 " II. Physical properties of minerals 75 " in. Chemical properties of minerals 102 " IV. Classification of minerals 129 PAET II. THE GEMS. Division of Gems 135 Color, gravity, and hardness 137 Chemical characters 139 Composition 139 Artificial production of Gems and Minerals 140 Geological characters 145 Geographical distribution 146 Practical division and nomenclature 147 History of Gems 148 Sculpture in Gems 151 On Grinding 153 Forms of the diamond 161 Form of Gems 163 Common lapidary ....... 166 Engraving 166 Sawing and drilling Gems fc 168 1* 10 CONTENTS. PAGB Grinding and polishing materials 168 Heightening the color of Gems 169 Setting of Gems 171 Cleaning Gems 172 Imitations of Gems 172 Price of, and trade in Gems '. . . . 181 Gems for optical purposes 181 PAET III. CONSIDERATION OF THE INDIVIDUAL GEMS. Diamond 183 Corundum 214 Sapphire 214 Common corundum 223 Chrysoberyl, Cymophane 225 Spinelle 227 Topaz 229 Euclase ' 234 Emerald 235 Beryl, aquamarine 240 Zircon, Hyacinth, Jargon 244 Garnet 247 Essonite, Cinnamon -stone 253 Tourmaline, Kubellite, Siberite 254 Quartz 259 Kock crystal 260 Amethyst 266 Common quartz rose quartz 269 " " Cat's eye 270 " " Prase 271 " " Avanturine 272 Jasper 273 Hornstone .....' 277 Chalcedony 277 Carnelian 279 Heliotrope, Bloodstone 282 Agate 283 Chrysoprase 292 CONTENTS. 11 PAGB Chrysolite, Peridot, Olivin 294 Isolite 297 Opal 299 Fire opal 304 Hydrophane 305 Semi-opal m 306 Cachelong 307 Jasper opal 308 Obsidian 309 Axinite % 311 Felspar 312 Adularia 312 Common felspar 315 Labrador 317 Hypersthene 320 Idocrase 321 Hauyne 322 Lapis lazuli 322 Kyanite, Sappare, Disthene 327 Turquoise 329 Natrolite 332 Fluor spar , 333 Malachite .336 Satin spar 340 Alabaster 341 Amber , 343 Jet 353 Meerschaum 357 Lava , 360 Jade ; 361 Serpentine -. 362 Marble 364 Stalactite and Stalagmite 380 Egyptian and Italian marbles 382 American marbles 383 Pisolite and Oolite 386 Rock of Gibralter 386 Apatite 387 Lepidolite 389 Mica.. . 389 12 CONTENTS. PA 08 Pyrites ... .. 390 Kose manganese 391 Porphyry 391 Sienite 393 Granite 396 Pearls , 400 Corals ......... 419 Shell cameos : 425 Mosaic and Pietra Dura.. . 426 INTRODUCTION. THE natural productions of our globe may be considered either in their original or in their changed condition. They are divided into two general classes which are determined, either by certain characters that do not require explana- tion or investigation, or, by the external appearances which are presented by them in their altered condition, and by investigating the causes which produced the changes of form or state. In the former case, the science is called Natural History; in the latter, Natural Philosophy. Natural History, considered in reference to the original properties of natural productions, must, therefore, be di- vided into organic and inorganic: to the former belong Zoology and Botany ; to the latter, Mineralogy. Botany and Zoology comprise bodies possessed of vitality, or beings which, increasing by the absorption of nutritive substances, mature after a certain period ; their parts are dependent upon each other, and they cannot be separated without destroying the integrity of the individual, which, after a certain period, loses its vitality and ceases to exist ; 14 INTRODUCTION. or death ensues, decomposition takes place, and the original being is entirely destroyed. Mineralogy, on the contrary, comprises those natural objects which are not possessed of life, and do not increase by absorption, but merely by accretion that is, by an ex- ternal growth or addition without any assimilation ; they do not mature by age ; their parts may be separated with- out destroying their individuality; and their formation being the result of chemical attraction, they are not liable to decomposition. Mineralogy comprises two distinct sciences : Mineralogy proper, which treats of the simple minerals, either as inde- pendent bodies, or in relation to the characters which serve to determine and distinguish them ; and G.eology, which considers both simple and mixed minerals as they exist in nature, and in their dependent relations with soils and rocks. Mineralogy describes the individual qualities of the several mineral species, Geology treats of them only- as associated in the structure of the earth. The characters of minerals are ascertained by their mor- phological, physical, and chemical properties. That part of Mineralogy which treats of the application of minerals to the different arts, is called Economical Mineralogy ; miner- als used by lapidaries in making ornaments, are called Gems. Geometry, Physics (Natural Philosophy), and Chemistry, form the base for the study of Mineralogy, as without a knowledge of those sciences, the true characters of a min- eral cannot be ascertained. Geology is, according to Lyell's explanation, the science which investigates the successive changes that have taken place in the organic and inorganic kingdoms of nature. It INTRODUCTION. 15 inquires into the causes of these changes, and the influence which they have exerted in modifying the surface and ex temal structure of our planet. By these researches into the state of the earth and its inhabitants at former periods, we acquire a more perfect knowledge of its present condi- tion, and* more comprehensive views concerning the laws now governing its animate and inanimate productions. When we study history, we obtain a more profound in- sight into human nature, by instituting a comparison be- tween the present and former states of society. We trace the long series of events which have gradually led to the actual posture of affairs, and by connecting effects with their causes, we are enabled to classify and retain in the memory a multitude of complicated relations, the various peculiarities of national character, the different degrees of moral and intellectual refinement, and numerous other cir- cumstances, which, without historical associations, would be uninteresting or imperfectly understood. When we carry back similar relations into the history of nature, we likewise investigate nature's operations in former epochs. The form of a coast, the configuration of the interior of a country, the existence and extent of lakes, valleys, and mountains, can often be traced to the former prevalence of earthquakes and volcanoes in regions which have long been undisturbed. To these remote convulsions the present fer- tility of some districts, the sterile character of others, the elevation of land above the sea, the climate, and various peculiarities, may be distinctly referred. Many distinguish- ing features of the surface of the earth may often be as- cribed to the operation, at a remote era, of slow and tran- quil causes, to the gradual deposition or sediment in a lake 16 INTRODUCTION. or in the ocean, or to the prolific increase of testacea and corals. "We also find in certain localities subterranean de- posits of coal, consisting of vegetable matter formerly drifted into seas and lakes. These seas and lakes have since been filled up, the lands whereon the forests grevt have disappeared or changed their form, the rivers and currents which floated the vegetable masses can no longer be traced, and the plants belonged to species which for ages have passed away from the surface of our planet, yet the commercial prosperity and numerical strength of a nation may now be mainly dependent on the local distribution of fuel determined By that ancient state of things. Geology is intimately connected to almost all physical sciences, as history is to the moral. An historian should, if possible, be profoundly acquainted with ethics, politics, jurispru- dence, the military art, theology, and with all branches of knowledge, by which an insight into human affairs, or into the moral and intellectual nature of man, can be obtained. No less desirable is it for a geologist to be well versed in chemistry, natural philosophy, mineralogy, zoology, com- parative anatomy, botany, and every science relating to organic and inorganic nature. Having such accomplish- ments, the historian and geologist would rarely fail to draw correct and philosophical conclusions from the various monuments transmitted to them from former occurrences. They would know to what combination of causes analogous effects were referable, and would often be enabled to sup- ply by inference information concerning many events unre- corded in the defective archives of former ages. Mineralogy is sometimes understood as comprising the natural history of every portion of inorganic nature. Here INTRODUCTION. 17 we consider it as limited to the natural history of simple minerals, or mineral species. In the strictest sense, a min- eral species is a natural inorganic body, possessing a defi- nite chemical composition, and assuming a regular deter- minate form, or series of forms. Many substances hereto- fore regarded as minerals will naturally be excluded such as all the artificial salts, the inorganic secretions of plants and apimals, the remains of former living beings now im- bedded in rocks. Many substances originally organic pro ducts have by common consent found a place in mineral systems such as coal, amber, and -mineral resins which ought not to be the case ; also some amorphous substances, with no forms or chemical composition, a*s some kinds of clay, have also been introduced into works on Mineralogy, but often improperly, and with no beneficial result. Aggre- gates of simple minerals or rocks are likewise excluded from the science of Mineralogy, though the various associations of minerals, their modes of occurrence, and their geologi- cal position, are important points in the history of the dif- ferent species. One most important object in Mineralogy is a full description of minerals, their essential properties and distinctive characters, as will enable the student to distin- guish the various species, and to. recognize them when they occur in nature. The gems, or precious stones, are obtained from miner- als. It is indispensable, therefore, to be fully acquainted with all the characters which distinguish them from one another, which is accomplished by the terminology or no- menclature of the science of Mineralogy that is, with the meaning of the terms used in describing the properties of minerals, and the various modifications they may undergo, 18 and also an account of the properties themselves. The system of classification is another closely related portion of Mineralogy. It gives an account of the order in which the mineral species are arranged. A third and most important part of Mineralogy is the physiography of the various species giving an account of their characteristic marks, and a description of their appearance or external aspect and forms, their principal physical and chemical properties, their mode of occurrence, with their geological and geo- graphical distribution, and their various uses, whether in nature or whether in tne arts, or as gems for ornamental purposes, PART I. TERMINOLOGY. CHAPTER I. FORM OF MIXERAIS. THE physical properties of a mineral comprise all those properties belonging to it as a body existing in space, and consisting of matter aggregated in a peculiar way. The more important of these are, its form as shown in crystal- lization ; its structure as determining its mode of cleavage and fracture ; its hardness and tenacity ; its weight or spe- cific gravity ; and its relations to light, heat, electricity, and magnetism. Crystalline and Amorphous. Mineral substances occur 'in two distinct modes of aggregation. Some consist of minute particles simply collected together, with no regu- larity of structure or constancy of External form, and are named amorphous. All fluid minerals are in this condition, together with some solid bodies, which appear to have con- densed either from a gelatinous condition like opal, when they are named porodine, or from a state of igneoue fluidity like, obsidian and glass, when they are named hyalite. The other class have their ultimate atoms evidently arranged according to definite law, and are named crystallim., when the regulai ity of structure appears only in the internal *is- 20 A PRACTICAL TREATISE ON GEMS. position of the parts ; and crystallized, when it also produces a determinate external form, or a crystal. CRYSTALS. Faces, Edges, Angles, Axes of Crystals. The word crystal in mineralogy designates a solid body exhibiting an original (not artificial) more or less regular polyhedric form. It is thus bounded by plane surfaces, named faces, which intersect in straight lines OY. edges, and these again meet in points . and form solid angles, bounded by three or more faces. The space occupied by a crystal is often named a form of crystallization, which is thus the mathematical figure regarded as independent of the matter that fills it. Crystals bounded by equal and similar faces are named simple forms / while those in which the faces are not equal and similar are named compound forms, or combinations, being regarded as produced by the union or combination of two or more simple forms. The cube or hexahedron (fig. 1), bounded by six equal and similar squares; the octahe- dron (fig. 2), by eight equilateral triangles ; and the rhom- bohedron, by six rhombs, are thus simple forms. An axis of a crystal is a line -passing through its centre and termi- nating either in the middle of two faces, or of two edges, or in two angles ; and axes terminating in similar parts of a crystal are named similar axes. In describing a crystal, one of its axes is supposed to be vertical or upright, and is then named the principal axis, and that axis is chosen which is the only one of its kind in the figure. A few other techni- cal terms used in describing crystals will be explained as they occur. . . Systems of Crystallization. The forms of crystals that occur in nature seem almost innumerable. On examining them, however, more attentively, certain relations are dis- FORM OF MINERALS. 21 covered even between highly complex crystals. When the axes are properly chosen, and placed in a right position, the various faces are observed to group themselves in a regular and beautiful manner around these axes, and to be all so related as to compose connected series produced according to definite laws. In every mineral species there is a certain form of crystal from which, as a primary, every other form of crystal observed in that mineral species may be deduced. In each species the axes, bearing to each other definite numerical proportions, intersect at angles which are constant. So also the faces of the various forms are related to each other, and to their primary, according to certain definite laws. When viewed in this manner, amd referred to their simplest forms, the innumerable variety of crystals occurring in nature may all be reduced to six distinct groups, or, as they are named, systems of crystallization. The following are the names given to these systems of crystallization in some of the best authors : Naumann. 1. Tesseral System. 2. Tetragonal System. 8. Hexagonal System. 4. Rhombic System." 5. Monoclinohedric System. 6. Triclinohedric System. In the following treatise the terminology of Naumann is adopted, his method of classifying and describing crystals appearing the simplest and best adapted to promote the progress of the student. Holohedric and Hemihedric. Before describing these systems, it must be observed that certain crystals appear as the half of others, and are therefore named hemihedric ; while the crystals with the full number of faces are named holohedric. Hemihedric crystals are formed when the alter- Mobs. Tessular. Pyramidal. Rhoinbohedral. Orthotype. Hemiorthotype. Anprthotype. Weiss and G. Eose; Regular. 2 and 1 axial. 3 and 1 axial. 1 and /I axial. 2 and 1 membered. 1 and 1 membered. 22 A PRACTICAL TREATISE ON GEMS. nate faces or groups of faces of a holohedric crystal increase symmetrically, so as to obliterate the other faces. Thus, if four alternate faces of the octohedron increase so as to obliterate the other four, a tetrahedron with half the num- ber of faces is formed. I. The first, or Tesseral System, named from tessera, a cube, wliich is one of the most frequent varieties, is charac- terized by three equal axes intersecting each other at right angles. Properly speaking, this system has no chief axis, as any one of them may be so named, arid placed upright in drawing and describing the crystals. Of these there are thirteen varieties, which are thus classed and named from the number of their faces : 1. One Tetrahedron, or form with four faces. 2. One Hexahedron, with six faces. 3. One Octahedron, with eight faces. 4. Four Dodecahedrons, with twelve faces. 5. Five Icosi tetrahedrons, with twenty-four faces. 6.r One Tetracontaoctahedron, with forty-eight faces. The dodecahedrons are further distinguished, according to the form of their faces, into rhombic, trigonal, deltoid, and pentagonal dodecahedrons ; and some of the icositetra- hedrons have also received peculiar names. Fig.1. Fig. 2 FORM OF MINERALS. 23 The following is a description, with figures, of the differ- ent forms above mentioned, beginning with The Hololiedric forms. 1. The hexahedron or cube (fig. 1) is bounded by sax equal squares, has twelve edges, formed by faces meeting at 90, and eight trigonal angles. The principal axes join the centre points of any two opposite faces. Examples are fluor spar, galena, boracite. 2. The octahedron (fig. 2), bounded by eight equilateral triangles, has twelve equal edges, with planes meeting at 109 28', and six tetragonal angles. * The principal axes join the opposite angles, two and two. Example, alum, spinel, magnetic iron ore. 3. The rhombic-dodecahedron (fig. 3) is bounded by twelve equal and similar rhombs (diagonals as 1 andv^2), Fig.* Fig. 4. has twenty-four equal edges of 120, and six tetragonal and eight trigonal angles. The principal axes join two opposite tetragonal angles. Ex., garnet, boracite. 4. The tetrakishexahedrons (variety of icositetrahedron, fig. 4) are bounded by twenty-four isosceles triangles, ar- ranged in six groups of four each. They have twelve longer edges which correspond to those of the primitive or in- 24 A PRACTICAL TREATISE ON GEMS. scribed tube, and twenty-four shorter edges placed over each of its faces. The angles are eight hexagonal and six tetragonal ; the latter joined two and two by the three prin- cipal axes. This form varies in general aspect, approach- ing, on the one hand, to the cube ; on the other, to the rhom- bic-dodecahedron. Ex., fluor spar, gold. 5. The triakisoctahedrons (variety of icositetrahedron, fig. 5) are bounded by twenty-four isosceles triangles, in eight groups of three, and, like the previous form, vary in general aspect from the octahedron on one side, to the rhombic-dodecahedron on .the other. The edges are twelve longer, corresponding with those of the' inscribed octahe- dron, and twenty-four shorter, three and three over each of the faces. The angles are eight trigonal and six dite- tragonal (formed by eight faces) ; the latter angles joined two and two by the principal axes. Ex., galena, diamond. Fig. 5. Fig. 6. 6. The icositetrahedrons (most common variety, fig. 6) are bounded by twenty-four deltoids or figures with .four . sides, of which two and two adjacent ones are equal. This form varies from the octahedron to the cube, sometimes approaching the former and sometimes the latter in general jispect. The edges are twenty-four longer and twenty- four shorter. The angles are six tetragonal joined by the FORM OF MINERALS. 25 principal axes, eight trigonal, and twelve rhombic, or tetra- gonal with unequal angles. 7. The hexakisoctahedrons (fig. 7), bounded by forty- eight scalene triangles, vary much in general aspect, ap- proaching more or less to all the preceding forms ; but most frequently they have the face? arranged either in six groups of eight, or eight of six, or twelve of four faces. There are twenty-four long edges, often corresponding to those of the rhombic-dodecahedron ; twenty-four interme- diate edges lying in pairs over each edge of the inscribed octahedron ; and twenty-four short edges in pairs over the edges of the inscribed cube. There are six ditetragonal angles joined by the principal axes, eight hexagonal and twelve rhombic angles. Ex., fluor spar, garnet, diamond. Fig. 7. The seven forms of crystals now described are related to each other in the most intimate manner. This will appear more distinctly from the following account of the derivation of the forms, with which is conjoined an explanation of the crystallographic signs or symbols by which they are desig- nated. We have adopted these symbols throughout this work, in the belief that they not only mark the forms in a greatly abbreviated manner, but also exhibit the relations of the forms and combinations in a way which words could hardly accomplish. 26 A PRACTICAL TREATISE OX GEMS. The derivation of forms is -that process by which, from one form chosen for the purpose, and considered as the type the fundamental or primary form all the other forms of a system may be produced, according to fixed prin- ciples or general laws. In order to understand this process or method of derivation, the student should keep in mind that the position of any plane is fixed when the positions of any three points in it, not all in one straight line, are known. To determine the position, therefore, of the face of a crystal, it is only necessary to know the distance of three points in it from the centre of the crystal, or the points in which the face or its supposed extension would in- tersect the three axes of the crystal. The portion of the axes between this point and the centre are named parame- ters, and the position of the face is sufficiently known when the relative length or proportion of these parameters is ascertained. When the position of one face of a simple form is thus fixed or described, all the other faces are in like manner fixed, since they are all equal and similar, and all intersect the axes in a uniform manner ; and the expres- sion which marks or describes one face, marks and describes the whole figure. The octahedron is generally adopted as the primary or fundamental form of the tessera! system, and distinguished by the first letter of the name, O. Its faces cut the half axes at equal distances from the centre ; so that these semi- axes, or the parameters of the faces, have to each other the proportion 1:1:1. In order to derive the other forms from the octahedron, the following construction is em- ployed. The numbers refer to the descriptions above. Suppose a plane so placed in each angle of the octahe- dron as to be vertical to the axis passing through that angle and consequently parallel to the two other axes (or to cut them at an infinite distance = 00); then the hexa- FORM OF MINERALS. 27 hedron or cube (l) is produced, designated by the crystal- lographic sign oo O oo ; expressing the proportion of the parameters of its faces, or oo : oo : 1. If a plane is sup- posed placed in each edge parallel to one axis, and cut- ting the two other axes at equal distances, the resulting figure is the rhombic dodecahedron (3), designated by the sign oo O, the proportion of the parameters of its faces be- ing oo : 1 : 1. The triakisoctahedron (5) arises when on each edge of the octahedron planes are placed cutting the axis not belonging to that edge at a distance from the cen- tre m which is a rational number greater than 1. The proportion of its parameters is therefore mil : 1, and its sign mO ; the most common varieties being f O, 2O, and 3O. When, on the other hand, from a similar distance m in each two semiaxes prolonged, a plane is drawn to the other semiaxis, or to each angle, an ikositetrahedron (6) is formed ; the parameters of its faces have consequently the proportion m : 1 : m, and its sign is mOm the most com- mon varieties being 2O2 and 303, the former very frequent in leucite, analcime, and garnet. When, again, planes are drawn from each angle, or the end of one semiaxis of the octahedron, parallel to a second axis, and cutting the third at a distance rc, greater than 1, then the tetrakishexahedron (4) is formed, the parameter of its faces oo : 1 : n ; its sign 3>On; and the most common varieties in nature ooOf, oc O2, and oo O3. Finally, if in each semiaxis of the octa- hedron two distances, m and ft, be taken, each greater than 1, and m also greater than n, and planes be drawn from each angle to these points, so that the two planes lying over each edge cut the second semiaxis belonging to that edge, at the smaller distance n, and the third axis at the greater distance m, then the hexakisoctahedron (7) is pro- duced, the parameters of which are m : n : 1, its sign mOn, and the most common varieties 3Of, 4O2, and 5Of . 28 A PRACTICAL TREATISE ON GEMS. The next class of crystals are the semi- tesseral form,s ; and first, those with oblique faces, often named tetrahedral, from their relation to the tetrahedron. (1.) This form (fig. 8) Fig. 8. Fig. 9. is bounded by four equilateral triangles, has six equal edges with faces meeting at 70 32 ', and four trigonal angles. The principal axes join the middle points of each two op- posite edges. Ex., gray-copper ore, boracite, and helvine. (2.) The trigonal dodecahedrons (fig. 9) are bounded by twelve isosceles triangles, and vary in general form from the tetrahedron to the hexahedron. There are six longer edges corresponding to those of the inscribed tetrahedron, and twelve shorter placed three and three over each of its faces ; and four hexagonal and four trigonal angles. Ex., gray-copper ore, and bismuth-blende. (3.) The deltoid- dodecahedrons (fig. 10) are bounded by twelve deltoids, and vary in general form from the tetrahedron on the one hand, to the rhombic-dodecahedron on the other. They have twelve longer edges lying in pairs over the edges of the inscribed tetrahedron ; and twelve shorter edges, three and three over each of its faces. The angles are six tetra- gonal (rhombic), four acute trigonal, and four obtuse tri- gonal angles. The principal axes join two and two oppo- site rhombic angles. Ex., gray-copper ore. (4.) The hex- akistetrahedrons (fig. 11) are bounded by twenty-four FORM OF MINERALS. 29 scalene triangles, and most commonly have their faces grouped in four systems of six each. The edges are twelve shorter and twelve longer, lying in groups of three over Fig. 10. Fig. 11. each face of the inscribed tetrahedron, and twelve interme diate in pairs over its edges. The angles are six rhombic, joined in pairs by the principal axes, and four acuter and four obtuser hexagonal angles. Ex., diamond. The derivation and signs of these forms are as follows : The tetrahedron arises when four alternate faces of the octahedron are enlarged, so as to obliterate the other four, and its sign is hence . But, as either four faces may be thus enlarged or obliterated, two tetrahedrons can be formed similar in all respects except in position, and together mak- ing up the octahedron. These are distinguished by the signs + and , added to the above symbol, but only the latter in general expressed thus . In ah 1 hemihedric systems two forms similarly related occur, which may thus be named complementary forms. The trigonal dodecahe- dron is derived from the icositetrahedron, by the expansion of the alternate trigonal groups of faces. Its sign is - , 30 A PRACTICAL TREATISE ON GEMS. 2O2 the most common variety being , found in gray-copper ore. The deltoid-dodecahedron is in like manner the result of the increase of the alternate trigonal groups of faces of the triakisoctahedron, and its sign is . Lastly, the hexakis- tetrahedron arises in the development of alternate hexa- gonal groups of faces in the hexakisoctahedron, and its sign . mOn ~' The parallel-faced semitesseral forms are two. (1.) The pentagonal dodecahedrons (fig. 12) are bounded by twelve Fig. 12. Fig. 13. symmetrical pentagons, and vary in general aspect be- tween the hexahedron and rhombic-dodecahedron. They have six regular (and in general longer) edges, lying over the faces of the inscribed hexahedron, and twenty- four generally shorter (seldom longer) edges, usually lying in pairs over its edges. The angles are eight of three equal angles, and twelve of three unequal angles. Each princi- pal axis unites two opposite regular edges. This form is derived from the tetrakishexahedron, and its sign is , one of the most common varieties being , found fre- quently in iron pyrites and cobaltine. (2.) The dyakisdo- FORM OF MINERALS. 31 decahedron (fig. 13), bounded by twenty-four trapezoids with two sides equal, has twelve short, twelve long, and twenty-four intermediate edges. The angles are six equi- angular rhombic, united in pairs by the principal axes, eight trigonal, and twenty-four irregular tetragonal angles. It is derived from the hexakisoctahedron, and its sign is F ' , J the brackets being used to distinguish it from the hexakiste- Fig. 14. Fig. 15. trahedron, also derived from the same primary form. It occurs in iron pyrites and cobaltine. There are two other tetrahedral forms, the pentagonal dodecahedron (fig. 14), and the pentagonal icositetrahedron (fig. 15), both bounded by irregular pentagons, but not yet observed in nature. Combinations. These forms of the tesseral system (and this is true also of the five other systems of crystallization) not only occur singly, but often two, three, or more are united in the same crystal, forming what are named combinations. In this case it is evident that no one of the individual forms can be completely developed, because the faces of one form must partially interfere with the faces of the other forms. A combination therefore implies that the faces of one form shall appear symmetrically disposed between the faces of other forms, and consequently in the room of certain of their edges and angles. These edges and angles are thus, 32 A PRACTICAL TREATISE ON GEMS. as it were, cut off, and new ones produced in their place, which properly belong neither to the one form nor the other, but are edges or angles of combination. Usually, one form predominates more than the others, or has more influence on the general aspect of the crystal, and hence is distinguished as the predominant form, the others being named subordi- nate. The following terms used on this subject require ex- planation. A combination is developed when all the forms contributing to its formation are pointed out ; and its sign consists of the signs of these forms, written in the order oi their influence on the combination, with a point between. An angle or edge is said to be replaced when it is cut ofl by one or more secondary planes ; it is truncated when cut by one plane, forming equal angles with the adjacent faces ; and an edge is bevelled when replaced by two planes, which are equally inclined to the adjacent faces. It will be readily seen that such combinations may be exceedingly numerous, or rather infinite ; and only a few of the more common can be noticed, simply as specimens of the class. Many others more complicated will occur in the descriptive part of this treatise. Among plenotesseral combinations, the cube, octahedron, and also the rhombic- dodecahedron, are the predominant forms. In fig. 16 the Fig. 16. Fig. 17. cube has its angles replaced by the faces of the octahedron, and the sign of this combination is ooOoo . O. In fig. 17 this process may be regarded as having proceeded still fur- FORM OF MINERALS. 33 ther, so that the faces of the octahedron now predominate, and the sign, of the same two elements but in reverse order, is O . ooOoo. In fig. 18 the cube has its edgesre placed Fig. la Fig. 19. by the faces of the rhombic-dodecahedron, the sign being oo Goo . ccO; while in fig. 19 there is the same combina- tion, but with the faces of the cube subordinate, and hence the symbol is ooO . ooOoo . The former figure, it will be seen, has more the general aspect of the cube ; the latter of the dodecahedron. In combinations of semitesseral forms with oblique faces, the tetahedron, the rhombic-dodecahedron, or even the hexahedron, seldomer a trigonal-dodecahedron, are the more Fig. 20. Fig. 2L common predominant forms. In fig. 20 two tetrahedrons in opposite positions, -^ are combined. In fig. 21 a 2* 34 A PRACTICAL TREATISE ON GEMS. very complex combination of seven forms is represented in a crystal of gray-copper ore, its full sign being (0 .ooOcc (/) . ^ (o). the letters in brackets connecting them with the respective faces of the figure. As examples of combinations of semi- tesseral forms with parallel faces, we may take fig. 22, in Fig. 22. Fig. 23. which each of the angles of the cube is unsymmetrically replaced by three faces of the dyakisdodecahedron, and hence ccOoo . I I ; or fig. 23, in which the pentagonal- dodecahedron has its trigonal angles replaced by the faces oo02 of the octahedron, consequently with the sign . O. Figure 24 represents the same com- bination but with greater predomi- nance of the faces of the octahedron, the crystal being bounded by eight equilateral and twelve isosceles tri- angles. II. Tetragonal System. This sys- tem has three axes at right angles, Fig. 24. two of them equal and one unequal. The last is the princi- pal axis, and when it is brought into a vertical position the crystal is said to be placed upright. Its ends are named FORM OF MINERALS. 38 poles, and the edges connected with them polar edges. The two other axes are named subordinate or lateral axes, and a plane passing through them is named the basis of the crystal. The two planes that pass through the principal and one of the lateral axes are named normal chief sections, and a plane through the chief axis intermediate to them, a diagonal chief section. The name tetragonal is derived from the form of the basis, which is usually quadratic. There are eight tetragonal forms, of which five are closed, that is, bounded on ah 1 sides by planes, and of definite extent, and three open, which in certain directions are not bounded, and consequently of indefinite extent. The description of the varieties is as follows, it being premised that a crystallographic pyramid is equivalent to two geometrical pyramids joined base to base. Fig. 25. Fig. 26. Closed forms. (1.) Tetragonal pyramids (figs. 25, 26) are inclosed by eight isosceles triangles, with four middle edges all in one plane, and eight polar edges. There are three kinds of this form, distinguished by the position of the lat- eral axes. In the first these axes unite the opposite angles ; in the second they intersect the middle edges equally; C A PRACTICAL TREATISE ON GEMS. and in the third they lie in an intermediate position, or divide these edges unequally ; the latter being hemihedral forms. These pyramids are also distinguished as obtuse (fig. 25) or acute (fig. 26), according as the vertical angle is greater or less than in the octahedron, which, though intermediate, is never a tetragonal form. (2.) Ditetragonal pyramids (fig. 27) are bounded by sixteen scalene triangles, Fig. 27. Fig. 28. whose base lines are all in one plane. This form rarely occurs except in combinations. (3.) Tetragonal sphenoids (fig. 28), bounded by four isosceles triangles, are the hemi- hedral forms of the first variety of tetragonal pyramids. (4.) The tetragonal scalenohedron (fig. 29), bounded by eight scalene triangles, whose bases rise and fall in a zig-zag line, is the hemihedral form of the ditetragonal pyramid. The latter two forms are rare. Open forms. Tetragonal prisms (fig. 30) bounded by four planes parallel to the principal axis; ditetragonal prisms by eight similar planes. In these prisms the prin- cipal axis is supposed to be prolonged infinitely, or to be unbounded. Where it is very short and the lateral axes FORM OF MINERALS. 87 infinite, the basal piriacoid is formed, consisting merely ot two parallel faces. The various series of tetragonal crystals are distinguished from each other only by their relative dimensions. To Fig. 29. Fig. 80. determine these, one of the series must be chosen as the fundamental form, and for this purpose a tetragonal pyramid of the first variety, designated by P as its sign, is selected. The angle of one of its edges, especially the middle edge, found by measurement, determines its angular dimensions ; while the proportion of the principal axis (a) to the lateral axes supposed equal to 1, gives its linear dimensions. The parameters, therefore, of each face of the fundamental form are 1 : 1 : a. Now if m be any (rational) number, either less or greater than 1, and if from any distance ma in the principal axis planes be drawn to the middle edge of P, then new tetra- gonal pyramids of the first kind, but more or less acute or obtuse than P, are formed. The general sign of these pyramids is mP, and the most common varieties ^P, 2P, 3P ; with the chief axis equal to ^, twice or thrice that of P. If m becomes infinite, or = o>, then the pyramid passes into a prism, indefinitely extended along the principal axis, A PBACTICAL TREATISE ON GEMS. and with the sign ooP; if m=0, which is the case when the lateral axes are supposed infinite, then it becomes a pinacoid, consisting properly of two basal faces, open to- wards the lateral axes, and designated by the sign OP. The ditetragonal pyramids are produced by taking in each lateral axis distances n greater than 1, and drawing two planes to these points from each of the intermediate polar edges. The parameters of these planes are therefore m : I : n, and the general sign of the form mPn, the most common values of n being J, 2, 3, and oo. When n = oo, a tetragonal pyramid of the second kind arises, designated generally by mP oo, the most common in the mineral kingdom being P oo and 2P oo. The relation of these to pyramids of the first Fig. 81. Fig. 32. kind is shown in fig. 31, where ABBBX is the first, and ACCCX the second kind of pyramid. In like manner from the prism ooP, the ditetragonal prisms ooPn are derived, arid finally when n = oo, the tetragonal prism of the sec- ond kind, whose sign is oopoo . The combinations of the tetragonal system are either holohedric or hemihedric ; but the latter are rare. Prisms and pinacoids must always be terminated on the open sides by other forms. Thus in fig. 32 a square prism of the first kind is terminated by the primary pyramid, and has its FORM OF MINERALS. 39 lateral angles again replaced by another more acute pyra- mid of the second kind, so that its sign is ooP . P . 2Poo. In fig. 33 a prism of the second kind is first bounded by Fig. 33. Fig. 84. the fundamental pyramid, and then has its edges of combi- nation replaced by a ditetragonal pyramid, and its sign is here ooPoo . P . 3P3. In fig. 34 the polar edges of the pyramid are replaced by another pyramid, its sign being P. Poo . In fig. 35 a hemihedric form very characteris- tic of copper pyrites is represented, P and P' being the two sphenoids, Fi s- ;35 - a the basal pinacoid, and 5, c, two ditetragonl pyramids. III. The Hexagonal System. The essential character of this system is, that it has four axes, three equal lateral axes intersecting each other in one plane at 60, and one principal axis at right angles to them. The extremities of the prin- cipal axis are named poles, and sections through it and one lateral axis, normal chief sections. The plane through the lateral axes is the basis, and from its hexagonal form gives the name to the system. As in the last system, its forms are either closed or open / and are divided into holohedral, 40 A PRACTICAL TREATISE ON GEMS. hemihedral, and tetartohedral, the last forms with only a fourth part of their faces developed. The tetartohedral and many of the hemihedral forms are of rare occurrence, and only a few of the more common require to be here described. The hexagonal pyramids (figs. 36, 37) are bounded by twelve isosceles triangles, and are of three kinds, according Fig. 36. Fig. 37. as the lateral axes fall in the angles, in the middle of the lateral edges, or in another point of these edges, the latter being hemihedral forms. They are also classed as acute or obtuse, but without any very precise limits. The trigo- nal pyramid is bounded by six triangles, and may be viewed as the hemihedral form of the hexagonal. The dihexago- nal pyramid is bounded by twenty-four scalene triangles, but has never been observed alone, and rarely even in com- binations. The more common prisms are the hexagonal of six sides, and the dihexagonal of twelve sides. As the fundamental form of this system, a particular pyr- amid P is chosen, and its dimensions determined either from the proportion of the lateral to the principal axis (1 : a), or from the measurement of its angles. From this form (mP) others are derived exactly as in the tetragonal POKM OF MINERALS. 41 system. Thus dihexagonal pyramids are produced with the general sign wPn, the chief peculiarity being that, whereas in the tetragonal system n might have any rational value from 1 to oo, in the hexagonal system it can only vary from 1 to 2, in consequence of the geometric charac- ter of the figure. When n=2 the dihexagonal changes into an hexagonal pyramid of the second kind, whose sign is raP2. When m is = oo various prisms arise from similar changes in the value of n ; and when w=0, the basal pina- coid. Few hexagonal mineral species form perfect holohedric combinations. Though quartz and apatite appear as such, Fig. 33. Fig. 39. yet properly the former is a tetartohedral, the latter a hem- ihedral species. In holohedric species the predominant faces are usually those of the two hexagonal prisms ooP and oo P2, or of the pinacoid OP; while the pyramids P and 2P2 are the most common subordinate forms. Figure 38 represents the prism, bounded on the extremities by two pyramids ; one, P, forming the point, the other 2P2, the rhombic faces on the angles, or ocP . P . 2P2. In some crystals the lateral edges of the prism are replaced by the 42 A PRACTICAL TREATISE ON GEMS. second prism o>P2, producing an equiangular twelve-sided prism, which always represents the combination ooP. ooP2, and cannot occur as a simple form. An example of a more complicated combination is seen in fig. 39, of a crystal of apatite, whose sign with the corresponding letters is ooP2(e) . OP(P) . $P(r) . P() . 2P(z) . P2() . Hexagonal minerals more frequently crystallize in those series of hemihedral forms that are named rhombohedral, from the prevalence in them of rhombohedrons. These are bounded by six rhombs (fig. 40), whose lateral edges do Fig 40. not lie in one plane, but vise and fall in a zig-zag manner. The principal axis unites the two trigonal angles, formed by three equal plane angles, and in the most common variety the secondary axes join the middle points of two opposite edges. When the polar edges form an angle of more than 90, the rhombohedrons are named obtuse ; when of less, acute. Hexagonal scalenohedrons (fig. 41) are bounded by twelve scalene triangles, whose lateral edges do not lie in one plane. The principal axis joins the two hexagonal angles, and the secondary axes the middle points of two opposite lateral edges. The rhombohedron is derived from the first kind of hexagonal pyramid by the hemihedric development of its alternate faces. Its general sign should therefore be ; 2 FORM OF MINERALS. 43 but on several grounds it is found better to designate it by R or raR, and its complimentary figure by niR. When the prism or pinacoid arise as its limiting forms, they are designated by ooR and OR, though in no respect changed from the limiting forms 00 P and OP of the pyramid. The scalenohedron is properly the hemihedric form of the dihexagonal pyramid, but is better derived from the inscribed rhombohedron mR. If the halves of the prin- cipal axis of this are multiplied by a definite number n^ Fig. 41. and then planes drawn from the extremities of this enlarged axis to the lateral edges of the rhombohedron, as in figure 42, the scalenohedron is constructed. Hence it is desig- nated by wiR", the n being written on the right hand, like an algebraic exponent : and the dihexagonal prism is in like manner designated by ooR". 44 A PRACTICAL TREATISE ON GEMS. The combinations of rhombohedric forms are very nu- merous, some hundreds being described in calc-spar alone. Among the more common is the prism in combination with a rhombohedron, as in the twin crystal of calc-spar (fig. 43), Fig. 48. Fig. 44. with the sign coR. iR, the lower half being the same form with the upper, but turned round 180. In figure 44, the rhombohedron mR has its polar edges replaced by Fig. 45. Fig. 46. another rhombohedron JwR ; and in figure 45 its lateral edges bevelled by the scalenohedron mR*. A more com- FORM OF MINERALS. 45 plex combination of five forms is represented in the crystal of calc-spar, fig. 46, its sign with the letters on the faces being R 5 (y) . R 3 (r) . R(P) . 4R(m) . oo R(c). Tetartohedric combinations are seen most distinctly in pure quartz or rock- crystal, the pyramids of the first kind appearing as rhom- bohedrons, those of the second kind as trigonal pyramids, the dihexahedral prisms as ditrigonal prisms, and the prism oo P2 as a trigonal prism. Most of these forms, however, occupy but a very subordinate place in the combinations which consist essentially of the prism ooP, and the rhom- p bohedron R . IV. Rhombic System. The rhombic system is charac- terized by three axes, all unequal, but at right angles to each other. One of these is assumed as the chief axis, when the others are named subordinate. The plane pass- ing through the secondary axes, or the basis, forms a rhomb, and from this the name is derived. This system comprises only a few varieties of forms that are essentially distinct, and its relations are consequently very simple. Fig. 47. Fig. 43. The closed forms are, (1st.) The rhombic pyramids (figs. 47, 48), bounded by eight scalene triangles, whose 46 A POPULAR TKEATISE ON GEMS. lateral edges lie in one plane, and form a rhomb. They have eight polar edges, four acute and four more obtuse. and four lateral edges, and six rhombic angles, the most acute at the extremities of the longest axis. (2cl) The rhombic sphenoids (fig. 49) are bounded by four scalene triangles with their lateral edges not in one plane ; and are a hemihedric form of the rhombic pyramid of unfrequent occurrence. The open forms again are, (3d.) Rhombic prisms bounded by four planes parallel to Fig. 49. one of the axes which is indefinitely extended. They are divided into upright and horizontal prisms, according as either the principal or one of the lateral axes is supposed to become infinite. For the latter form the name doma or dome has been used ; and two kinds, the macrodome and the brachydome, have been distinguished. Rhombic pinacoids also arise when one axis becomes =0, and the two others are indefinitely extended. In deriving these forms from a primary, a particular rhombic pyramid P is chosen, and its dimensions determined either from the angular measurement of two of its edges, or by the linear proportion of its axes a : b: c\ the greater lateral axis b being assumed equal to 1. To the greater lateral axis the name macrodiagonal is frequently given ; to the shorter, that of brachydiagonal ; and the two princi- pal sections are in like manner named macrodiagonal and brachydiagonal, according to the axis they intersect. The same terms are applied throughout all the derived forms, where they consequently mark only the position of the faces in respect to the axes of the fundamental crystal, FORM OF MINERALS. 47 without reference to the relative magnitude of the derived axes. By multiplying the principal axis by any rational num- ber m, greater or less than 1, a series of pyramids arise, whose general sign is mP, and their limits the prism and pinacoid, the whole series being contained in this formula, OP rnP P - mP ooP ; which is the fundamental series, the lateral axes always remaining unchanged. From each member a new series may, however, be developed in two directions by increas- ing one or other of the lateral axes. When the macrodia- gonal is thus multi- plied by any number n greater than 1, and planes drawn from the distance n to the polar edges, a new pyramid is produced, named a macropyra- mid, with the sign wP/i, the mark over the P pointing out the axis enlarged. When M=QO a ma- crodome results, with the sign mPoo . If the shorter axis is multiplied, then bra- chypyramids and brachydomes are produced with the signs ?nPn and mPcc . So also from the prism ooP, on the one side, numerous macroprisms ooP^, with the limiting ma- Fig. 50. Fig. 51. 48 A POPULAR TREATISE 05* GEMS. cropinacoid coPoo; on the other, numerous brachyprisma ooPft,, with the limit form ooPoo, or the brachypinacoid. In figs. 50, 51, the two domes are shown in their relation to the primitive pyramid. The pyramids seldom occur independent, or even as the predominant forms in a combination, sulphur, however, being an exception. Prisms or pinacoids usually give the general character to the crystal, which then appears either in a columnar or tabular, or even in a rectangular pyramidal form. The determination of the position of these crystals, Fig. 52. Fig. 54. as vertical or horizontal, depends on the choice of the chief axis of the fundamental form. In the topaz crystal (fig. 52) the brachyprism and the pyramid are the predominant ele- ments, associated with the prism, its sign and letters being ooP2(Q . P(o) . ooP(m). Fig. 53 of stilbite is another ex- ample, the macropinacoid co Poo or M, being combined with the pyramid P(?"), the brachypinacoid ooPoo (T), and the basal pinacoid OP (P). Another instance is fig. 54 of a lievrite crystal, where the brachyprism and pyramid com- bine with the macrodome, or coP2 . P . Poo . The follow- ing figures are very common forms of barytes ; figs. 55 and FORM OF MINERALS. 49 Fig. 55. Fig. 53. 56 being both composed of the pinacoid, a brachydome, and macrodome, with sign OP (c).Poo(/)iPoo(d),the variation in aspect arising from the predominance of different faces ; and fig. 57 consisting of the macro- dome -|P oo , the prism a>P(^), and the pinacoid OP. V. The Monodinohe- dric System. This system is characterized by three unequal axes, two of which intersect each other at an oblique angle, and are cut by the third at right an- gles. One of the oblique axes is chosen as the chief axis, and the other axes are then distinguished as the orthodiagonal (right-angled) and clino- diagonal (oblique-angled). The same terms are applied to the chief sections, and the name of the system refers to the fact that these two planes and the base, together with two right angles, form also one oblique angle C. The forms of this system approach very near to those of the rhombic series, but the inclination of the axes, even when almost a right angle, gives them a peculiar character, by which they are always readily distinguished. Each pyramid thus separates into two altogether independent forms or hemipyramids. Three varieties of prism also oc- cur, vertical, inclined, and horizontal, with faces parallel to the chief axis, the clinodiagonal or the orthodiagonal. The horizontal prisms, like the pyramids, separate into two independent partial forms, named hemiprisms or hemi- 3 Fig. 57. 50 A POPULAR TREATISE ON GEMS. domes. The inclined prisms are often designated clino- domes, the term prism being restricted to the vertical forms. Orthopinacoids and clinopinacoids are also distin- guished from their position in relation to the axes. The monoclinohedric pyramids (fig. 58) are bounded by A eight scalene triangles of two kinds, four and four only be- ing similar. Their lateral & edges lie all in one plane, and the similar triangles are placed in pairs on the clino- diagonal polar edges. The two pairs in the acute angle between the orthodiagonal and basal section are desig- nated the positive hemipyra- mid ; while the two pairs in the obtuse angles of the same sections form together the negative hemipyramid. But as these hemipyramids are wholly independent of each other, they are rarely observed combined. More frequently each occurs alone, and then forms a prism-like figure, with faces parallel to the polar edges, and open at the extremities. Hence, like all prisms, they can only appear in combination with other forms. The vertical prisms are bounded by four equal faces parallel to the principal axis, and the cross section is a rhomb ; the clinodomes have a similar form and section ; while the horizontal prisms or domes have unequal faces, and their section is a rhomboid. The mode of derivation of these forms closely resembles that of the rhombic series. A complete pyramid is as- sumed as the fundamental form, and designated =b P, in order to express the two portions of which it consists. Its dimensioRS a.re given when the proportion of its axes $;: c, FORM OF MINERALS. 51 and the angular inclination of the oblique axes (7, which is also that of the orthodiagonal section to the basis, are known. The fundamental series of forms is OP dbwP P mP ooP ; from each of whose members, by changing the dimensions of the other axes, new forms may be again derived. Thus from mP, by multiplying the orthodiagonal by any number n, a series of orthopyramids rtraP/*, is produced with the orthodomes raPoo , as limiting forms. The clinodiagonal produces a similar series, distinguished from the former by the sign being put in brackets, thus, db(wPw), with the limiting clinodome ( mP ) always completely formed, and therefore without the signs attached. From o>P arise ortho- prisms oo Ptt, and the orthopinacoid ooPoo; and clino- prisms (ooPtt), and the clinopinacoid (ooPoo). The combinations of this system may be easily under- stood from their resemblance to those of the rhombic ; the chief difficulty being in the occurrence of partial forms, which, however, closely resemble the hemihedric forms of the previous systems. We shall therefore only select a few examples frequently observed in the mineral kingdom. Fig. 59 represents a very common form of gypsum crystals Fig. 59. Fig. 60. (ooPoo) (P) . ooP(/) . P(&). The most common form of augite is represented in fig. 60, with the sign ct>P(m) . 52 A POPULAR TREATISE ON GEMS. oo Poo (r) . ( ooPoo ) (I) . P(s). Fig. 61 is a crystal of com mon felspar or orthoclase, composed of the clinopinacoid (ooPoo) (Jf), the prism ooP(f T ), the basal pinacoid OP (P), and the hemidomes 2P (y) : to which, in fig. 62 of Fig. 61. Fig. 62. the same mineral, the hemipyramid P(o), and the clino- dome ( 2Poo ) (rc), are added. VI. Tridinohedric System. This is the least regular of all the systems, and departs the most widely from symmetry of form. The axes are all unequal, and inclined at angles none of which are right angles, so that to determine any crystal or series of forms the proportion of the axes a : b : c, and also their angles, or those of the inclination of the chief sections, must be known. As in the previous system, one axis is chosen as the principal axis, and the two others dis- tinguished as the macrodiagonal and brachydiagonal axes. In consequence of the oblique position of the principal sec- tions, this system consists entirely of partial forms wholly independent on each other, and each composed only of two parallel faces. The complete pyramid is thus broken up into four distinct quarter pyramids, and the prism into two hemiprisms. Each of these partial forms is thus nothing more than a pair of parallel planes, and the various forms consequently mere individual faces. This circumstance FORM OF MINERALS. 53 renders many triclinohedric crystals very unsymmetrical in appearance. Triclinohedric pyramids (fig. 63) are bounded by eight triangles, whose lateral edges lie in one plane. They are equal and parallel two and two to each other ; each pair forming, as just stated, a tetartopyramid or open form, only limited by combination with other forms, or, as we may sup- pose, by the chief sections. The prisms are again either vertical or in- clined ; the latter named domes, and their section is always rhomboidal. In deriving the forms, the fundamental pyramid is placed upright with its brachy- diagonal axis to the spectator, and the .partial forms desig- nated, the two upper by 'P and P', the two lower by ,P and P y , as hi the figure. The further derivation now follows as in the rhombic system, with the modifications already mentioned, so that we need not delay on it longer, especially as the minerals crystallizing in these forms are not numerous. Fig. 63. Fig. 64 Some combinations of this system, as the series exhibited by most of the felspars, approach very near to the mono- clinohedric system ; while others, as the blue copper, 01 A POPULAR TREATISE ON GEMS. vitiiol, and axinite, show great incompleteness and want of symmetry. In the latter case the determination of the forms is often difficult and requires great attention. As specimens, we may notice the albite crystal (fig. 64), in which P is the basal piuacoid OP; J/the brachydiagonal pinacoid ooPco; s the upper right pyramid P'; Zthe right hemiprism ooP'; T the left hemiprism oo'P; and x the hemidome 'P'oo . Figures 65 and 66 are crystals of axinite, Fig. 65. Fig. 6G. the former from Dauphine, the latter very common in Corn- wall, of whose faces the following is the development : r the macropinacoid ooPoo ; P the left hemiprism co'P; u the left upper quarter pyramid 'P ; I the left upper quarter pyramid 2'P; s the left upper partial form of the macro- pyramid 3'P3 ; and x the hemidome 2'P,oo . Imperfections of Crystals. In the foregoing description of the forms of crystals the planes have been supposed smooth and even, the faces equal and uniform, or at the same distance from the centre or point of intersection of the axes, and each crystal also perfect or fully formed and complete on every side. In nature, however, these conditions are rarely if ever real- ized, and the edges of crystals are seldom straight lines, or the faces mathematical plane surfaces. A very interesting variety of these irregularities, which pervades all the sys- tems except the tesseral, is named hemimorphism. In this FORM OP MIXEEALS. 55 the crystals are bounded on the opposite ends of their chiet axis by faces belonging to distinct forms, and hence only the upper or under half of each form is produced, or the crystal, as the name implies, is half-formed. Figure 67 rep- resents a common variety of tourmaline, bounded on the Fig. 67. Fig. 63. upper end by the planes of the rhombohedrons R and 2R, and on the lower end by the basal piuacoid. In fig. 68 of electric calamine the upper extremity shows the basis &, two brachydomes o and p, and two macrodomes m and l\ while on the lower end it is bounded by ;the faces P of the primary form. This appearance becomes more interesting from the fact that most hemimorphic crystals acquire polar electricity from heat, that is, exhibit opposite kinds of electricity at opposite ends of the crystal. The faces of crystals are very frequently rendered im- perfect by striae, or minute linear and parallel elevations and depressions. These arise in the oscillatory combination of two crystal forms, alternately prevailing through small spaces. The striae, therefore, are in reality the edges of combined forms. They are very common on quartz, shorl, and some other minerals ; and frequently indicate combina- tions where only a simple form would otherwise appear to exist. The cubes and pentagonal dodecahedrons of iron 56 A POPULAR TREATISE ON GEMS. pyrites are frequently striated, and in three directions at right angles to each other. In calc-spar the faces of the rhombohedron, JR (g in fig. 43 above) are almost never without striae parallel to the oblique diagonal. The stria- tion is said to be simple when only one series of parallel lines appears on each face, or feathered when two systems diverge from a common line. In other crystals the faces, then said to be drusy, are covered by numerous projecting angles of smaller crystals; an imperfection often seen in fluor spar. The faces of crystals occasionally appear curved either, as in tourmaline and beryl, from the peculiar oscil- latory combination mentioned, or by the union of several crystals at obtuse angles, like stones in a vault, as in stilbite and prehnite. A true curvature of the faces probably oc- curs in the saddle-shaped rhombohedrons of brown spar and siderite, in the lens-like crystals of gypsum, and in the curved faces so common on diamond crystals. In chabasite similar curved faces occur, but concave. In galena and augite the crystals are often rounded on the corners, as if by an incipient state effusion. On other crystals the faces are rendered uneven from inequalities following no certain rule. These imperfections furnish valuable assistance in develop- ing very complex combinations, all the faces of each indi- vidual form being distinguished by the same peculiarity of surface. Irregularities in the forms of crystals are produced when the corresponding faces are placed at unequal distances from the centre, and consequently differ in form and size. Thus the cubes and octahedrons of iron pyrites, galena, and fluor spar, are often lengthened along one axis. Quartz is subject to many such irregularities, which are seen in a very remarkable manner on the beautiful transparent and sharply angular crystals from Dauphine. In such irregular forms, instead of one line, the axes are then represented by an FOKM OF MINERALS. 57 infinite number of lines, parallel to the ideal axis of the figure. The same irregularity carried to a greater extent frequently causes certain faces required for the symmetry of the form, altogether to disappear. Again, some crystals do not fill the space marked out by their outline, holes and vacancies being left in the faces, occasionally to such an extent that they seem little more than mere skeletons. This appearance is very common on crystals produced ar- tificially, as in common salt, alum, bismuth, silver, &c. A perfect crystal can only be produced when, during its for- mation, it is completely isolated, so as to have full room to expand on every side. Hence the most perfect crystals have been originally imbedded singly in some uniform rock mass. Next to them in perfection are forms that grow singly, on the surface of some mass of similar or distinct composition, especially when the point of adherence is small. An incompleteness of form, or at least a difficulty in determining it, arises from the minuteness of some crys- tals, or from their contracted dimensions in certain direc- tions. Thus some appear mere tabular or lamellar planes, while others run out into acicular, needle-shaped, or capil- lary crystals. Amid all these modifications of the general form of the crystal, of the condition and aspect of its indi- vidual faces, or of its linear dimensions, one important ele- ment, the angular measurement, remains constant. In some monoaxial crystals, indeed, increase of temperature produces an unequal expansion in different directions, slightly chang- ing the relative inclination of the faces, but so small as to be scarcely perceptible in common measurements, and hence producing no ambiguity. More important are the angular changes which in many species accompany slight changes in chemical composition, particularly in the relative propor- tions of certain isomorphous elements. But notwithstand- ing these limitations, the great truth of the permanence of 58 A POPULAR TREATISE ON GEMS. the angular dimensions of crystals, announced by Rome de 1'Isle, remains unaffected; only, as Mohs well states, it must not be interpreted with a rigid immutability, incon- sistent with the whole analogy of other parts of nature. The Goniometer and Measurement of Crystals. The fact just stated of the permanence of the angular di- mensions of crystals, shows the importance of some accurate method of measuring their angles ; that is, the inclination of two faces to each other. Two instruments have been specially used for this pur- pose, the common or contact goniometer, invented by Ca- ringeau, and the reflecting go- niometer of Wollaston. The former is simply two brass rulers turning on a common centre, between which the crystal is so placed that its faces coincide with the edges of the rulers, and the angle is then measured on a graduated arc. This instrument is suffi- ciently accurate for many pur- poses and for large crystals ; but for precise determination is far inferior to the reflecting goniometer. This requires smooth and even faces, but Fig. 69. these may be very small, even the hundredth of an inch, in skilful hands ; and as small crystals are generally most perfect, far greater accuracy can FORM OF MINERALS. 59 be attained, and the measurement depended on to one minute (!'). The reflecting goniometer is represented in fig. 69. It consists essentially of a graduated circle mm, divided on its edge into twice 180, or more often into half degrees, the minutes being read off by the vernier hh. This circle turns on an axis connected with ft, so that by turning this the circle is moved round, but is stopped at 1 80, when moving in one direction, by a spring at k. The other part of the instrument is intended to attach and adjust the crystal to be measured. The first axis of mm is hollow, and a second axis, , passes through it from ss, so that this and all the connected parts from b tof can be turned without moving the circle mm. The axis d passes through a hole in be, so that it can turn the arm de into any required position ; f is a similar axis turning the arm og ; and pq a fourth axis, in like manner movable in g, and with a small knob at q, to which the crystal to be measured is attached. When about to use the instrument, it should be placed on a table, with its base horizontal, which is readily done by the screws in it, and opposite to a window at about 12 or 15 feet distance, so that its axis shall be parallel to the horizontal bars of the window. One of the upper bars of the window, and also the lower bar, or, instead of the lat- ter, a white line on the floor or table parallel to the window, should then be chosen in order to adjust the crystal. The observer places himself behind the instrument with the side a at his right hand. The crystal is then attached to q by a piece of wax, with the two faces to be measured upward. The axis fo is made parallel to o#, and the eye being brought near to the first face of the crystal, the axes aa and p are turned till the image of the window is seen re- flected in the face with the horizontal and vertical bars in their position. The axis d is then turned through a con- 60 A POPULAR TREATISE ON GEMS. siderable angle (say 60), and the image of the window again sought and brought into its proper place by turning the axis/", without moving p. When this is done, that face is brought into its true position, normal to d, so that no motion of d can disarrange it. Hence the image of the window may now be sought in the second face and brought into its true position, with the horizontal bars seen horizon- tal, by moving the axes d and a. When this is done the crystal is properly adjusted, and the angle is thus measured. First bring the zero of the circle and vernier to coincide, and then turn the inner axis a or as, and move the eye till the image of the upper bar of the window reflected from the more distant face of the crystal coincides with the lower bar or horizontal line seen directly. Keeping the eye in its place, turn the outer axis tt till the reflected image of the upper bar in the other face in like manner coincides with the lower line, and the angle of the two faces is then read off on the divided circle. As the angle measured is not directly that of the faces, but of the rays of light re- flected from them, or the difference of the angle wanted from 180, the circle has the degrees numbered in the re- verse direction, so as to give the angle without the trouble of subtracting the one from the other. The above apparatus for adjusting the crystal is an im- provement suggested by Naumann. In the original instru- ment the axis fo was made to push in or out in a sheath, and had a small brass plate, bent at right angles, inserted in a cleft at o, to which the crystal was attached. The crys- tal was adjusted, as formerly, by moving the plate, or the axis/b, and by slight motion of the arm de, which should be at right angles nearly to be when used. A considerable improvement is, to have a small mirror fixed on the stand below the crystal, with its face parallel to the axis aa, and inclined at 45 to the window, when the lower line can be FORM OF MINERALS. 61 dispensed with, and the instrument used for various other purposes of angular measurement. Many alterations have been suggested for the purpose of insuring greater accuracy, but the simple instrument is sufficient for all purposes of de- terminative mineralogy, and the error from the instrument will in most cases be less than the actual variations in the dimensions of the crystals. Greater simplicity is indeed rather desirable, and the student will often find it sufficient to attach the crystal by a piece of wax to the axis a directly, and give it the further adjustment by the hand. The only use of the parts from b to q is to enable the observer to place the crystal properly ; that is, with the edge to be measured parallel to the axis of the instrument, and as nearly as possible coinciding with its centre. This is effected when the reflection of the horizontal bar in the two faces appears parallel to that edge. Modes or Twin Crystals. When two similar crystals of a mineral species are united with their similar faces and axes parallel, the one forms merely a continuation or enlargement of the other, and every crystal may be regarded as thus built up of a num- ber of smaller crystals. Frequently, however, crystals are united according to precise laws, though all their similar faces and axes are not parallel, and then are named macles or twin crystals. In one class of macles the axes of the two crystals are parallel, and in another they are inclined. The former only occur among hemihedric forms, and the two crystals are then combined in the exact position in which they would be derived from or reproduce the pri- mary holohedric form. The second class, with oblique axes, occur both in holohedric and hemihedric forms, and the two individuals are placed in perfect symmetry to each 62 A POPULAR TREATISE ON GEMS. other, in reference to a particular face of the crystal which forms the plane of union, or the equator of the made. We may also suppose the two crystals originally parallel, and the one turned round the normal of the united faces by 180 (often 90 or 60), while the other is stationary. Or we may suppose a crystal cut into halves in a particular direc- tion, and one half turned 1 80 on the other ; and hence the name of hemitrope given to them by Hauy. The position of the two individuals in this case corresponds with that of an object and its image in a mirror, whose surface then represents the plane of union. The manner in which the crystals unite also differs. Some are merely opposed or in simple contact ; others are, as it were, grown together, and mutually interpenetrate, occasionally so completely as to appear like one individual. The twin edges and angles in which the two unite are often re-entering ; or they may coincide in one plane, when the line of union is either imperceptible, or is only marked by the meeting of two systems of striae, or other diversity in the physical characters of the two faces. The formation of twin crystals may be again repeated, forming groups of three, four, or more. When the faces of union are parallel to each other, the crystals form rows of indeterminate extent; where they are not parallel, they may return into each other in circles, or form bouquet-like or other groups. Where crystals are merely in juxtaposi- tion, they are sometimes much shortened in the direction of the twin axis ; and where many occur in a series with parallel position, are often compressed into very thin plates, frequently not thicker than paper, giving to the surface of the aggregate a peculiar striated aspect. Only a few twin crystals in the different systems can be noticed, chiefly as examples of this mode of formation. In the tesseral system, forms that unite with parallel axes pro- F011M OF MINERALS. 63 duce intersecting macles like the pentagonal dodecahedrons of iron pyrites in fig. 70, and the tetrahedrons of gray-cop- Fig. 70. Fig. 71. per or fhhlore in fig. 71, a similar formation also occurring ' in the diamond. In macles with inclined axes the two forms almost always unite by a face of the octahedron, and the two individuals are then generally apposed and short- ened in the direction of the twin axis by one half, so that they appear like a crystal that has been divided by a plane parallel to one of its faces, and the two halves turned round on each other by an angle of 180. In this manner two octahedrons of the spinel, magnetic iron ore, or automolite Fig. 72. Fig. 73. (fig. 72), are frequently united. The same law prevails in the intersecting cubes of fluor spar, iron pyrites, and galena, 64 A POPULAR TREATISE ON GEMS. represented in fig. 73. In fig. 74 of zinc-blende, two rhom- bic dodecahedrons are united by a face of the octahedron. In the Tetragonal system, twin crystals with parallel axes Fig. 74. Fig. 75. rarely occur, but are seen in chalcopyrite, and one or two other minerals. Where the axes are inclined the plane of union is very often one of the faces of the pyramid Poo , or one of those faces that would regularly replace the polar edges of the fundamental form P. The crystals of tin ore obey this law, as seen in fig. 75, where the individuals are pyramidal, and in the knee-shaped crystal (fig. 76), where Fig. 76. Fig. 77. they are more prismatic. Hausmanite appears like fig. 77, in which the fundamental pyramid P prevails, on whose polar edges other crystals are often very symmetrically repeated. FORM OF MINERALS. 65 a central individual appearing like the support of all the others. Almost identical forms occur in chalcopyrite. In the Hexagonal system, twin crystals with parallel axes are common, as in calc-spar, chabasite, hematite, and other rhombohedric minerals. In calc-spar they often form very regular crystals, the two individuals uniting by a plane parallel to the base, so as to appear like a single crystal, as in fig. 78, where each end shows the forms ooR. R, but in a complementary position ; or in fig. 79 of two scaleno- hedrons R 3 from Derbyshire. The rhombohedric crystals of chabasite often appear intersecting each other, like those of fluor spar in fig. 73. The purer varieties of quartz or Fig. 78. Fig. 79. Fig. 80. rock crystal, in consequence of the tetartohedric character of its crystallization, often exhibit twins. In these the pyramid P separates into two rhombohedrons P and z, which, though geometrically similar, are yet physically distinct. In fig. 80 the two individuals are only grown to- gether, but more commonly they penetrate each other in an irregular manner, forming apparently a single crystal. Twins with oblique axes are also common, the plane of union being usually one face of the rhombohedron. Thus in calc-spar two rhombohedrons are often joined by a face 66 A POPULAR TREATISE ON GEMS. of gll, the two axes forming an angle of 127 34'; occa- sionally a third individual is interposed in a lamellar form, as in fig. 81, when the two outer crystals become parallel. Fig. 81. Fig. 82. This latter arrangement is very common in the highly cleavable varieties of Iceland spar. When the crystals unite in a face of the rhombohedron R, fig. 82, they form an angle of 89 8', differing little from a right angle, by which the occurrence of this law is very easily recognized, especially in prismatic varieties. In the rhombic system, twin crystals with parallel axes are very rare, but those with oblique axes common, the plane of union being one of the faces of the prism GO P. Twins of this kind are very distinctly seen in arragonite, Fig. S3. Fig. 84 Fig. 85. carbonate of lead, marcasite, stephanite, mispickel, and other minerals. In arragonite the crystals partly interpen- FORM OF MINERALS. 6-7 etrate, partly are in mere juxtaposition, as in fig. 83, where the individuals are formed by the Combination ooP(Jlf) . oo Poo (A), Poo (&), and in figure 84 where several crystals of the same combination form a series with parallel planes of union ; the inner members being so shortened that they appear like mere lamellar plates producing striae on the faces Poo and ooPoo of the made. In fig. 85 four crystals, each of the combination ooP . 2Poo , having united in in- clined planes, form a circular group, returning into itself. The carbonate of lead often occurs in macles in all respects Fig. 86. Fi ? . 87. similar. In staurolite, individuals of the prismatic combi- tion oo P . oo Poo . OP, combine either, as in fig. 86, by a face of the braehydome |Poo , with their chief axes almost at right angles; or, as in fig. 87, by a face of th brachypyramid f P|, the chief axes and the brachypina- coids (o) of the two single crystals meeting at an angle of about 60. Finally, in fig. 88, two harmotome crystals of the most common combination ooPoo . ooPoo . P . Poo , intersect each other so nearly at right angles, that their principal axes seem to Fig.88. coincide, and the brachypiuacoid (q) of the one crystal 68 A POPULAR TREATISE ON GEMS. (with a rhombic striae) is parallel to the macropinacoid (q) of the other. In -the monoclinohedric system the most common macles are those in which the principal axes and the chief sections of the two crystals are parallel to each other, and conse- quently the principal axis is also the twin axis. Usually the two individuals are united by a face parallel to the or- thodiagonal chief section, as in figure 89 of gypsum, where two crystals of the combination (ooPco).ooP. P, shown in fig. 59, unite so regularly that the faces of the pinacoids (P and P') form only one plane. In a similar manner the augite crystals of the combination ooP. ooPoo . (ooPoo). P, represented singly in fig. 60, are in fig. 90 united in a Fig. 89. Fig. 90. Fig. 91. macle so very symmetrical and regular that the line of junction cannot be observed on tlie face of the clinopinacoid. The two hemipyramids P (s) (like P (I) in the gypsum crystal above) form on one side a re-entering, on the other a salient angle. Hornblende, wolfram, and other minerals exhibit a similar appearance. In other cases the individuals partially penetrate each other, being, as it were, crushed together in the direction of the orthodiagonal. This mode of union is not uncommon in gypsum, and very frequent in orthoclase felspar. Two crystals of the latter, of the com- FOKM OF MINERALS. 69 bination ( ooPoo ) . ooP . OP . 2Poo , as in fig. 61 above, are often pushed sidewise into each other, as shown in fig. 91. In the triclinohedric system, some twin formations are of great importance as a means of distinguishing the triclino- hedric from the monoclinohedric species of felspar. In one variety the twin axis is the normal to the brachydiagonal chief section. But in the triclinohedric felspars this sec- tion is not, as it is in the monoclinohedric species, perpen- dicular to the basis, and consequently the two bases form on one side a re-entering, on the other a salient angle ; whereas in the monoclinohedric felspars (where the brachy- diagonal chief section corresponds to the clinodiagonal), no twin crystals can be produced in conformity to this law, and the two bases fah 1 in one plane. The albite and oligoclase very often exhibit such twins, as in figure 92, where the Fig. 92. very obtuse angles formed by the faces of OP, or P and P' (as well as those of 'P'oo , or x and #'), are a very charac- teristic appearance, marking out this mineral at once as a triclinohedric species. Usually the twin formation is re- peated, three or more crystals being combined, when those in the centre are reduced to mere plates. When very nu- merous, the surfaces P and x are covered with fine striae, often only perceptible with a microscope. A second law A POPULAR TREATISE ON GEMS. Fig. 93. observed in triclinohedric felspars, particularly the albite and labradorite, is that the twin axis corresponds with that normal of the brachydiagonal which is situated in the plane of the base. In pericline, a variety of albite, these twins appear as in fig. 93, where the two crys- tals are united by a face of the basal pinacoid P, while the faces of the two brachypinacoids (Jffand M') form edges with very obtuse angles (1*73 22'), re- entering on the one side and salient on the other. These edges, or the line of junction between JbTand Jtf' 9 are also parallel to the edges formed by these faces and the base, or those between M and P. In this case also the macles are occasionally sev- eral times repeated when the faces appear covered with fine stria3. Irregular Aggregation of Crystals. Besides the regular unions now described, crystals are often aggregated in peculiar ways, to which no fixed law can be assigned. Thus some crystals, apparently simple, are composed of concentric crusts or shells, which may be removed one after the other, always leaving a smaller crys- tal like a kernel, with smooth distinct faces. Some speci- mens of quartz from Beeralston in Devonshire consist ap- parently of hollow hexagonal pyramids placed one within another. Other minerals, as fluor spar, apatite, heavy spar, and calc-spar, exhibited a similar structure by bands of dif- ferent colors. Many large crystals, again, appear like an aggregate of numerous small crystals, partly of the same, partly of dif- ferent forms. Thus some octahedrons of fluor spar from Schlaggenwald are made up of small dark violet-blue cubes, FORM OF MINERALS. 71 whose projecting angles give a drusy character to the faces of the larger form. Such polysynthetic crystals, as they may be called, are very common in calc-spar. A similar, but still more remarkable formation, is where two crystals of distinct species are conjoined. Such unions of cyanite and staurolite have been long well known, and the graphic-granite exhibits a similar union between large felspar crystals and many smaller ones of mica and quartz. Forms of Crystalline Aggregates. Crystals have often been produced under conditions preventing the free de- velopment of their forms. They then compose crystalline aggregates, of which the following may be distinguished : Granular, formed of grains, generally angular, but rarely rounded or flattened. Lamellar consist of broad plates, which are tabular when of uniform thickness, lenticular when becoming thinner on the edges, icedge-shaped when sharpened towards one edge, and scaly when the plates are very small. Columnar, in which the individuals are drawn out in one direction more than in the others ; bacittary or rod-like, in which the columns are of uniform thickness ; acicular or needle-shaped,, in which they are pointed; and fibrous, in which they are very fine. In the broad-colum- nar the columns are, as it were, compressed, or broader in one direction than the other. The distinctions of large, coarse, small, or fine-granular ; thick or thin scaly ; straight, curved, or twisted- columnar ; parallel, diverging, or con- fused-fibrous ; and such like, are easily understood. Aggregates which have been able to crystallize, at least, with a certain degree of freedom, have been distinguished by Mohs into crystal groups and druses : the former includ- ing all unions of several imbedded crystals ; the latter those of crystals that have grown together on a common support. In the groups, crystals with their faces otherwise perfect are conjoined in various ways. Sometimes they radiate, as 72 A POPULAR TREATISE ON GEMS. it were, from a common centre, and produce spheroidal, el- lipsoidal, or other forms, frequent in gypsum, iron pyrites, and other minerals imbedded in clay. Where many such masses are united, they are named botryoidal when like bunches of grapes, mammellated where the spheres are larger and less distinct, and reniform or kidney-shaped where the masses are still larger. Some groups are par- tially attached by a small point ; but the mass is generally free. Crystals are often grouped in rows or in one direction, forming, when they are very small, capillary or hair-like, and filiform, thread, or wire-like forms, which are common among native metals, as gold, silver, copper, and bismuth, in silver glance and a few other materials. Sometimes the masses are dentiform, consisting of portions resembling teeth ; as is very common in silver. Often these groups expand in several directions, and produce arborescent, dendritic, foliated, feathered, or other forms, very common in copper. In these groups, however, a certain dependence on the crystallographic character of the species may be observed. The lamellar minerals often form fan-shaped, wheel-like, almond-shaped, comb-like, or other groups. The fibrous types, again, are disposed in parallel or diverg- ing bundles, or in radiating, stellar, and other masses. Coralloidal (like coral), fruticose (like cauliflower), and other forms, have also been observed. In druses, many crystals rise side by side from a common support ; sometimes only the granular mass composed of their united bases, at other times some distinct body. The form of a druse is determined by that of the surface on which it grows, and consequently is often very irregular or wholly accidental. Where completely inclosed they have been named drusy cavities, and when of a spheroidal form, geodes. A drusy crust, again, consists of a thin layer of FORM OF MINERALS. 73 small crystals investing the surface of a large crystal or" of some othep body. The minute or cryptocrystalline minerals form similar aggregates. In the globular or the oolitic, the minute crys- tals often appear to radiate from a centre, or form concen- tric crusts. Somewhat -similar are the stalactites and sta- lagmites, in which the mineral, especially rock-salt, lime- stone, chalcedony, opal, limonite, has been deposited from a fluid dropping slowly from some overhanging body. In this case the principal axis of the figure, generally a hollow tube, is vertical, while the individual parts are arranged at right angles to this direction. In other cases the mineral has. apparently been deposited from a fluid mass moving slowly in a particular direction, which may be regarded as the chief axis- of the figure, while the axes of the indi- vidual crystals may assume a different position. By far the largest masses of the mineral kingdom have, however, been produced under conditions in which a free development of their forms was excluded. This has been the case with the greater portion of the minerals compos- ing rocks or filling veins and dykes. The structure of these masses on the large scale belongs to geology, but some varieties of the texture visible even in hand specimens may be noticed. The individual grains or masses have seldom any regular form, but appear round, long, or flat, according .to circumstances, and as each has been more or less checked in the process of formation. Even then, however, a cer- tain regularity in the position of the parts is often observ- able, as in granite, in which the cleavage planes, and con- sequently the axes of the felspar crystals, are parallel. Where these grains are all pretty similar in size and shape, the rock is named massive when they are small, or granular when they are larger and more distinct. Sometimes the rock becomes slaty, dividing into thin plates ; or concretionary, 4 74 A POPULAR TREATISE ON 'GEMS. forming roundish masses ; at other times the interposition of some foreign substance (gas or vapor) has renderetl it porous, cellular or vesicular, giving rise to drusy cavities. These cavities are often empty, but have occasionally been filled by other minerals, when the rock is named amygda- loidal, from the almond-like shape of the inclosed masses. Many of the above external forms appear also in the amorphous solid minerals, in which no trace of individual parts, and consequently of internal structure, is observable. They are not unfrequently. disposed in parallel or concen- tric layers, of uniform or distinct colors ; and may assume spherical, cylindrical, stalactitic, and other appearances. Pseudomorphism. When the substance of one mineral assumes the external form of some other mineral, it is named a.pseudomorph. In some named incrusting pseudomorphs the original crystal is covered by a rough or drusy surface of the second mineral, frequently not thicker than paper. Occasionally the first crystal has been removed, and noth- ing but the shell remains ; or the cavity has been filled by a distinct mineral species, or a crystalloid, as it may .be named, forming an exact representation of the original, but of a different substance. More commonly the new mineral substance has gradually expelled the old, and replacing it, as it were, atom by atom, has assumed its exact form. In other cases not the whole substance of the original crystal, but only one or more of its elements, has been changed, or the whole matter has remained, but in a new condition. Thus arragonite crys- tals have been converted into calc-spar, the chemical com- position of both being identical ; or gaylussite has been changed into calc-spar, andalusite into cyanite, by the loss of certain elements. On the other hand, anhydrite be- comes gypsum, red-copper . ore malachite, by addition of new matter. Or-tho elements are partially changed, as . FORM OP MINERALS. 75 felspar T-to kaolin, quartz or pearl spar into talc, iron pyrites or iron glance into brown-iron ore> azurite into malachite, augite into green earth. The true nature of such bodies is shown by the internal structure, having no relation to the external form or apparent system of crystallization. The process of petrifaction of organic bodies is in reality a species of pseud oinorphic formation, and lias been pro- duced in all the above modes. External and internal casts of organic bodies are not uncommon. In other cases the original substance has been replaced by some mineral which has preserved not merely the external form, but ev'en the "minutest detail of internal structure ; so that the different kinds of wood have been distinguished in their silicified trunks. The most common petrifying substances are silica and carbonate of lime. In encrynites, echinites, belemnites, and other fossils, the crystals of calc-spar often occur in very regular positions. In some varieties of petrified wood both the ligneous structure and the cleavage of the calc- spar are observable. Different from the above are mineralized bodies, in which the original structure is still retained, but their chemical nature partially changed. In these a complete series may be often traced, as from wood or peat, through the varie- ties of brown coal, common coal, anthracite, and graphite, perhaps even to the diamond. CHAPTER II. PHYSICAL PROPERTIES OF MINERALS. THE physical characters of minerals comprehend, 1st. Those properties derived from the nature of the substance itself, as coherence, mode of fracturej elasticity, and density 7G A POPULAR TREATISE ON" GEMS. . or specific gravity ; 2cl Those phenomena called forth in minerals by the influence of some external power or agent, as their optical, electric, or thermal relations; and, 3d. Other characters depending on the personal sensation of the observer on his taste, smell, and touch. All these properties furnish useful characters in distinguishing and describing mineral species. Cleavage and Fracture. In many species there are certain planes at right* angles to which cohesion seems to be at a minimum, so that the mineral separates along or parallel to these planes far more readily than in any other direction. This property is named cleavage, and these planes cleavage-planes. They have a strictly definite position, and do not show any transition or gradual passage into the greater coherence in other direc- tions. The number of these parallel cleavage-planes is alto- gether indefinite ; so that the only limit that can be as- signed to the divisibility of some minerals, as gypsum and mica, arises from the coarseness of our instruments. These minima of coherence or cleavage-planes are always parallel to some face of the crystal, and similar equal mini- ma occur parallel to every other face of the same form. Hence they are always equal in number to the faces of the form, and the figures produced by cleavage agree in every point with true crystals, except that they are artificial. They are thus most simply and conveniently described by the same terms and signs as the faces of crystals. Some minerals cleave in several directions parallel to the faces of different forms, but the cleavage is generally more easily obtained and more perfect in one direction than in the others, This complex cleavage is well seen in calc-spar and fluor spar, and very remarkably in zinc-blende, where PHYSICAL PROPERTIES OF MINERALS. 77 it takes place in no less than six directions. As in each of these the division may be indefinitely continued, it is clear that no lamellar structure in any proper sense can be as- signed to the mineral. All that can be affirmed is, that contiguous atoms have less coherence in the normal of these planes than in other directions. When the cleavage takes place in three directions, it of course produces a perfect crystal form, from which the system of crystallization and angular dimensions of the species may be discovered, and is thus often of very great importance. The common cleavage in the different systems is as fol- lows, those of most frequent occurrence being put in italics. (1.) In the tessera), Octahedric, O, along the faces of the octahedron ; Bexahedric, ooOoo , alonij those of the cube , and Dodecahedric, o>O. (2.) In the tetragonal system, Pyramidal, P or 2Poo ; Prismatic, ooP or ooPoo; or Ba- sal, OP. (3.) In the hexagonal system with holohedric forms, Pyramidal, P or P2 ; Prismatic, ooP or ooP2 ; or Basal, OP ; with rhombohedral forms, EhomboJiedric, R ; Prismatic, oo R ; or Basal, OR. (4.) In the rhombic sys- tem, Pyramidal, P; Prismatic, ooP; Makro or Brachy- domatic, Poo or Poo; Basal, OP; Macrodiagonal, ooPoo; or Br 'achy 'diagonal, ooPoo . (5.) In the monoclinohedric system, Hemipyramidal, P or P; Prismatic, ooP; Clin- odomatie (P^o) ; Hemidomatic, Poo or Poo; Basal, OP; Orthodiagonal, ooPoo; or Clinodiagonal (ooPoo). (6.) In the triclinohedric system, Hemiprismatic, ooP' oroo'P; Hemidomatic either along the macrodome or brachydome ; Basal, OP; Macrodiagonal, ooPoo; or Br achy diagonal, 00 P 00. . In some minerals the cleavage is readily procured ; in others only with extreme difficulty. The planes produced also vary much in their degree of perfection, being highly perfect in some, as mica and gypsum ; imperfect in others, 78 A POPULAR TREATISE ON GESTS. as garnet and quartz. In a very few crystalline minerals cleavage-planes can hardly be said to exist. Cleavage must be carefully distinguished from the planes of union in twin crystals, and the division-planes in the laminar minerals. Fraeture surfaces are formed when a mineral breaks in a direction different from the cleavage-planes. They are consequently most readily observed when the cleavage is least perfect. The form of the fracture is named conchoidal when composed of concave and convex surfaces like shells, even when nearly free from inequalities. The character of the surface is smooth / or splintery when covered by small wedge-shaped splinters adhering by the thicker end; or hackly when covered by small slightly-bent inequalities, as in iron and other malleable bodies ; or earthy when it shows only fine dust. Hardness and Tenacity. The hardness of minerals, or their power of resisting any attempt to separate their parts, is also an important charac- ter. As it differs considerably in the same species, accord- ing to the direction and the surface on which the trial is made, its accurate determination is difficult, and the utmost that can usually be obtained is a mere approximation found by comparing different minerals one with another. For this purpose Mobs has given the following scale : 1. Talc, of a white or greenish color. 2. Rock-salt, a pure cleavable variety, or semi-transparent uncrystallizea gypsum,, the transparent and crystallized varieties being generally too soft. 8. Calcareous spar, a cleavable variety. 4. Fluor spar, in which the cleavage is distinct. 5. Apatite,\.\\Q asparagus-stone, or phosphate of lime. 6. Adularia felspar, any cleavable variety. 7. Rock- crystal, a transparent variety. 8. "Prismatic topaz, any simple variety. 9. Corundum, from India, which affords smooth cleavage surfaces. 10. The Diamond. PHYSICAL PROPERTIES OF MINERALS. 79 Two other degrees are obtained by interposing foliated mica between 2 and 3, and scapolite, a crystalline variety, between 5 and 6. The former is .numbered 2'5, the lat- ter 5*5. To ascertain the hardness of a mineral, first try which of the members of the scale is scratched by it, and in order to save the specimens, begin with the highest numbers, and proceed downward, until reaching one which is scratched. Then take a finer hard file, and draw along its surface, with the least possible force, the specimen to be examined, and also that mineral in the scale whose hardness is immediately above the one which has been scratched. From the resist- ance they offer to the file, from the noise occasioned by their passing along it, and from the quantity of powder left on its surface, their relative hardness is deduced. When, after repeated trials, we are satisfied to which member of the scale of hardness the mineral is most nearly allied, we say its hardness (suppose it to be felspar) is equal to 6, and write after it H.=:6'0. If the mineral do not exactly cor- respond with any degree of the scale, but is found to be between two of them, it is marked by the lower with a de- cimal figure added. Thus, if more than 6 but less than 7, it is expressed H.=6'5. In these experiments we must be careful to employ specimens which nearly agree in form and size, and also as much as possible in the shape of their angles. Where the scale of hardness is wanting, or for a first rough determination, the following experiments may serve : Every mineral that is scratched by the finger-nail has H. = 2-5 or less. Minerals that scratch copper have H. = 3 or more. Polished white iron has H. = 4-5. JVindow-glass has H. = 5 to 5*5. Steel point or file has H. = 6 to 7. Hence every mineral that will cut or scratch with, a good penknife has H. less than 6. 80 A POPULAR TREATISE ON GEMS. Flint has H. = 7, and only about a dozen minerals, including the precious atones or gems, are harder. Precious stones have latterly been divided and arranged according to their hardness, in the following three classes > 1. HARD OEMS ; OB THOSE HARDER THAN QUARTZ. Diamond. Topaz. Sapphire. Emerald. Ruby. Hyacinth. Chrysoberyl. Essonite. Spinelle. Garnet. 2. SEMI-HARD JEWELS. Eock Crystal. Opal. Amethyst. Chrysolite Chalcedony. Lazulite. Carnelian, and other Obsidian, similar ones. Turquoise. 3. SOFT PRECIOUS STONES. Those softer than Fluor-spar ; Malachite, Amber, and Jet. Closely allied to hardness is the TENACITY of minerals, of which the following varieties have been distinguished : A mineral is said to be brittle when, as in quartz, on attempt- ing to cut it with a knife, it emits a grating noise, and the particles fly away in the form of dust. It is sectile or mild when, as in galena and some varieties of mica, on cutting, the particles lose their connection in a considerable degree ; but this takes place without noise, and they do not fly off, but remain on the knife. And* a mineral is said to be soft or 'ductile when, like native gold or lead, it can be cut into slices with a knife, extended under the hammer, and drawn into wire. From tenacity it is usual to distinguish f rang I- bility) or the resistance which minerals oppose when we at- tempt to break them into pieces or fragments. This prop- erty must not be confounded with, hardness. Quartz is hard, and hornblende comparatively soft ; yet the latter is PHYSICAL PROPERTIES OP MINERALS. 81 || more difficultly frangible than the former. Flexibility again expresses the property possessed by some minerals of bending without breaking. They are elastic, like mica, if, when bent, they spring back again into their former di- rection ; or merely flexible, when they can be - bent in dif- ferent directions without breaking, but remain in their new position, as gypsum, talc, asbestus, and all malleable min- erals. Specific Gravity. The density or the relative weight o*f a mineral, com- pared with an equal volume of pure distilled water, is named its specific gravity. This is a most important character for dis- tinguishing minerals, as it varies considerably in different species, and can be readily ascertained with much accuracy, and in many cases without at ah 1 injuring the specimen. The whole process con- sists in weighing the body, first in air, and then immersed in water, the difference in the weight being that of an equal bulk of the latter fluid. Hence, assuming, as is com- monly done, the specific gravity of pure distilled water to be equal . Fig. 94. to 1 or unity, the specific gravity (G) of the other body is equal to its weight in air (w), di- vided by the loss or difference (G) of weight in water (or G=5. A simple and portable instrument for finding the specific gravity is a hydrometer of Nicholson, fig. 94. A delicate hydrostatic balance gives the gravity with far more 40 82 A POPULAR TREATISE ON GEMS. accuracy; and even a good common balance is often pief- erable. The mineral may be suspended from one arm or scale by a fine silk thread or hair, and its weight ascer- tained, first in the air, and then in water. There are a few precautions necessary to insure accuracy. Thus, a pure specimen must be selected which is not inter- mixed with other substances, and when weighed in air it should be quite dry. It must also be free from cavities, and care must be taken that when weighed in water no globules of air adhere to its surface, which render it lighter. If the body imbibos moisture, it should be allowed to re- main till fully saturated before determining its weight when immersed, and it is sometimes even necessary to boil the specimen in order to expel the air from its pores. Small crystals or fragments, whose freedom from mixture can be seen, are best adapted for this purpose. The specimen experimented on should not be too heavy ; thirty grains being enough where the gravity is low, and even less where it is high. It is also of importance to repeat the trial, if possible with different -specimens, which will show whether any cause of error exists, and to take the mean of the whole. A correction should be made for the variation of the temperature of the water from 60 Fahr., which is that usually chosen as the standard in mineralogical works. Where the difference, however, does not exceed ten or fif- teen degrees, this correction may be neglected, as it only affects the third or second decimal figure of the result. By determining the specific gravity of minerals with the hydrostatic balance, we proceed, for instance : an unknown, mineral having been weighed first in the air, and then fast- ened by means of a hair and weighed in water. Such as in the air 17 "65; in water 12*35. The loss in water is, therefore, 5 '30; and this number indicates the loss of so much bulk of water displaced by the mineral putting the PfiYSICAL PROPERTIES OF MINERALS. 83 specific gravity of water 1*00: x dividing 5 into 17'65, make it equal to 3 '5 3, which is the exact specific gravity of the mineral, and which is that of essonite. Instead of a hydrostatic balance, we may as "well use Nicholson's hy- drometer, a simple and A^ery convenient instrument, cot> sisting of a hollow glass cylinder (A), and two dishes (B and C) filled with lead, in order to keep the instrument upright. The hydrometer is put-in a glass vessel (E), filled with water, and used as follows : 1st. The weight is determined which is required to sink the instrument to the mark D in water. 2d. The mineral is put in the dish A over the weight noted, that 'is required, in addition to the mineral, to sink the hydrometer to D. 3d. The same experiment is repeated by putting the mineral, after being moistened and washed with water, in the dish C ; and now is A B the weight of the mineral in the air, and B b the weight of a quantity of water equal in volume to that of the mineral. For instance, let A = 32'8 B = 7-3 C = 15'8 there is (A b) 32*8 7*3 = 25*5 the weight of the mineral in the air. (C b) 15*8 7*3 = 8*5 the weight of an equal quantity of water, and proceed 8*5 : 25*5 = 1 : x 8-5 = 3*00, which is the proper specific gravity. For determining the specific gravity of substances or minerals lighter than water, or which float in water, it is necessary to adhere to the same method by the hydrome- ter. A heavier body, such as lead, after determining the 84 A POPULAR TREATISE ON GEMS. difference of weight, within or without the water, of both together, and then of the heavier body alone, the specific gravity of the lighter substance is the result. And for de- termining the specific gravity of liquids, by means of the hydrostatic balance, a glass ball is applied to one of the arms (its loss of weight in pure water being known), and, dipping the same in the liquid to be examined, any addition and abstraction will result in the specific gravity of the liquid. The hydrometers of Beaume for the different liquids to be examined, are employed with satisfactory results. That the specific gravity has been known as far back as the thirteenth century, and applied by the Oriental nations for determining the character of precious stones, is suffi- ciently proved by a work written in that century by Mo- hammed Ben Manner. In fact, the specific gravity is often, in connection with the color, quite essential in determining a gem. Optical Properties of Minerals. There are few more interesting departments of science than the relations of mineral bodies to light, and the modi- fications which it undergoes either when passing through them or when reflected from their surface. In this place, however, we can only notice these phenomena so far as they point out distinctions in the internal constitution of minerals, or furnish characters for distinguishing one species from another. Minerals, and even different specimens of the same spe- cies, vary much in pellucidity or in the quantity of light which can pass through them. Some transmit so much light, that small objects can be clearly seen, or letters read when placed behind them, and are named transparent. They are semi-transparent when the object is only seen PHYSICAL PROPERTIES OF MINERALS. 85 dimly, as through a cloud ; and translucent when the light that passes through it is so obscured that the objects can be no longer discerned. Some minerals are only thus trans lucent on the thinnest edges, and hi others even these trans mit no light, and the body is named opaque or untranspa rent. These degrees pass gradually into each other, and cannot be separated by any precise line ; and' this is also the case in nature, where some minerals pass through the whole scale, as quartz, from the fine transparent rock-crys- tal to opaque dark-black varieties. Such minerals may be described generally as pellucid. This change often arises from some mixture in their composition, especially of me- tallic substances. Perfect opacity is chieny found in the metals or their compounds with sulphur, though even these seem to transmit light when reduced to Iamina3 of sufficient thinness. Double Refraction. When a ray of light passes ob- liquely from one medium into another of different density, it is bent or refracted from its former course. The line which it then follows forms an angle with the perpendicu- lar, which in each body bears a certain proportion to that at which the ray fell upon, it ; or, as definitely stated, the sine of the angle of refraction has a fixed ratio to the sine of the angle of incidence, this ratio being named the index of refraction. This simple refraction is common to all transparent bodies, whether crystalline, amorphous, or fluid ; but some crystals produce a still more remarkable result. The ray of light which entered them as one is divided into two rays, each following different angles, or is doubly re- fracted. In minerals of the tesseral system this property does not exist, but it has been always observed in minerals belonging to the other systems, though in many only after they have been cut in a. particular manner, or have been otherwise properly prepared. It is most distinctly seen in 86 A POPULAR TREATISE ON GEMS. crystals of calc-spar, especially in the beautiful transparent variety from Iceland, in which it was first observed and described by Erasmus Bartholin in a work published at Copenhagen in 1669. The subjoined figure will illustrate this singular proper- ty. It represents a rhomb of Iceland spar, on the surface of which a ray of light E r falls. As seen in the figure, this ray divides into two, one of which rod follows the ordi- nary law of refrac- tion, or the sines of the angles of incidence and refraction maintain a constant ratio. This is named the ordinary ray O. The other, hence named the extraordinary ray E, does not obey the usual law of the sines, and has no general index of refrac- tion. In the plane perpendicular to the axis it is most widely separated from the ordinary ray, but in others ob- lique to it approaches nearer to O, and in one at right angles coincides, or there is no double refraction. This plane, or rather direction, in which there is no double re- fraction, is named the optical axis of the crystal, or the axis of double refraction. Now, in certain minerals, it is found that there is only one plane with this property, where- as in others there are two such planes, and they have in consequence been divided into monoaxial and binaxial. To the former (monoaxial) belong all crystals of the tetrago- nal and hexagonal systems ; to the latter (binaxial) all those of the three other systems. In the former the optic axis coincides with, or is parallel to, the crystallographic PHYSICAL PKOPEKTIES OF MINERALS. 87 chief axis. In some crystals the index of refraction for the extraordinary ray E is greater than for the ordinary ray O ; and in others it is smaller. The former are said to have positive (or attractive), the latter negative (or repulsive), double refraction. Quartz is an example of the former, the index of refraction, according to Malus, being for O= T5484, for E=l*5582; and calc-spar of the latter, the index of O being= 1*6543, of E=l*4833. The index of E is in both cases taken at its maximum. According to Dufrenoy, the following table shows the index of refraction of a great number of minerals : Chromate of lead ................................ 2-500 to 2-974 Diamond ........................................ 2-439 to 2'755 Native sulphur ................................... 2-115 Carbonate of lead ................................. 2-084 Zircon ........................................... 1-950 Garnet ........................................... 1-815 Spinelle .......................................... 1-812 Blue corundum (sapphire).. . ...................... 1*794 Red " (ruby) ...... '. ..................... 1-779 White " (sapphire) ........................ 1-768 Adularia ......................................... 1-764 Cymophane (oriental chrysolite) .................... 1-760 Boracite .......................................... 1-701 Carbonate strontia ................................ 1*700 Carbonate lime i extraordinary ray one of the rays .................... 1*635 , the other ray ..................... 1'620 ( ordinary ray .......................... 1-693 Arragomte { i extraordinary ray ..................... I'o3o ( Sulphate baryta J J { one of the rays ..................... 1*640 Yellow topaz -I , .. tfon { the other ray ....................... 1 '632 White topaz ...................................... l'10 the rays ....................... 1'624 J ie i ordinary ray * 1*642 1 extraordinary ray 1*663 r ordinary ray 1'548 Quartz { extraordinary ray *..1'558 88 A POPULAR TREATISE ON GEMS. Eock salt 1-557 Chalcedony 1'553 Gypsum 1 '525 Opal 1-479 Borax . 1 '475 Alum 1'457 Fluor spar 1*486 The higher the index of refraction, the more valuable appear to be the individual minerals, as may be seen by the corundum and topaz. Double refraction, whether positive or negative, being inherent in the respective mineral substances, forms a very ' important distinctive character, and the following minerals are arranged according to this property : CRYSTALS WITH ONE AXIS AND NEGATIVE DOUBLE EEFBACTION. Iceland spar. Anatase. Dolomite. Tourmaline. Carbonate iron. . Kubellite. Carbonate zinc. Corundum. Meionite. Emerald. Somervillite. Phosphate lime. Edingtonate. Idocrase. Wernerite. Mellite. Mica. Arseniate copper. Phosphate lead. Nepheline. Arseniate " Eed silver. Molybdate " Dioptase. Cinnabar. Alum. CRYSTALS WITH ONE AXIS AND POSITIVE DOUBLE REFRACTION. Zircon. Hydrate magnesia. Quartz. Eutil. Hydroxide iron. Oxahverite. 'Oxide tin. Calcareous Scheelite. Apophyllite. Iron. It should be observed that the optic axes are not single lines, but directions parallel to a line, or innumerable par- PHYSICAL PROPERTIES OF MINERALS. 89 allel lines, passing through every atom of the crystal. It is also important to remark that this property divides the systems of crystallization into three precise groups, the tesseral, with single refraction ; the tetragonal and hexago- nal, with double refraction, and monoaxial ; the other three systems also double, but binaxial. It is therefore of use to determine the system to which a mineral belongs, but is not of great value as a character for distinguishing species. Polarization of Light. Intimately connected with this property is that of the polarization of light, which being more easily and precisely observable than double refraction, is in many cases of higher value as a mineralogical character. By this term is meant a peculiar modification which a ray of light undergoes, in consequence of which its capability of being transmitted or reflected towards particular sides is either wholly or partially destroyed. Thus, if from a transparent prism of tourmaline two thin plates are cut parallel to its axis, they will transmit light, as well as the prism itself, when" they are placed above each other with the chief axis of both in the same direction. But when the one slip of tourmaline is turned at right angles to the other, either no light at all or very little is transmitted, and the plates consequently appear black. Hence, in passing through the first slip the rays of light have acquired a pe- culiar property, which renders them incapable of being transmitted through th*e second, except in a parallel posi- tion, and they are then said to be polarized. The same property is acquired by a ray of light when reflected, at an angle of 35^ (or angle of incidence 54^), from a plate of glass, one side of which is blackened, or from some other non-metallic body. When such a ray falls on a second similar mirror at an equal angle, but so that the plane of reflection in the second is at right angles to that in the first, it is no longer reflected, but wholly absorbed. 90 A POPULAR TREATISE ON GEMS. When, on the other hand, the planes of reflection are parallel, the ray is wholly and at any intermediate angle partially reflected. A ray of light polarized by reflection is also incapable of transmission through a tourmaline slip in one position, which, however, is' at right angles to that in which a ray polarized by passing through another slip is not transmitted. In order to observe the polarization of light, a very sim- ple instrument will be found useful (fig. 96). At one end of a horizontal board B a black mirror a is fixed. In the middle is a pillar to which a tube c d is fastened, with its axis directed to the mirror at an angle of 35. On the lower end is a cover c, with a small hole in the centre, and at the upper end another cover with a small black mirror m attached to it by two arms, as in the figure, and also at an angle of 35 . With this instrument the mirror m can be so placed in relation to a that the planes of reflection shall have any desirable inclination to exhibit the simple polarization of light. . This instrument furnishes a simple test whether minerals that cleave readily into, thin lamella? are optically mono- axial or binaxial. Place the two mirrors with their, polari- zation-planes at right angles, and fix a plate of the mineral with a little wax over the hole c, and then observe what takes place in the second mirror during the time that the cover c is turned round. If the mineral belongs to the bi Fig. 96. PHYSICAL PROPERTIES OP MINERALS. 91 naxial system, the light from the first mirror , in passing through it, is doubly refracted and has its polarization changed, and consequently can be again reflected from the second mirror m, and in each revolution of.c will show four maxima and four minima of intensity. If, on the contrary, the mineral is monoaxial,\the ray will pass through the lami- na unaltered, and will not be reflected from the second mir- ror in any position of c. Another beautiful phenom- enon of polarized light, in like manner connected with the crystalline structure of miner- als, is the colored rings which Fig. 98. Fig. 99. laminse of the doubly-refracting species, when of a proper th ckness, exhibit in certain positions. These rings are 92 A POPULAR TREATISE ON GEMS. easily seen in the above apparatus by interposing a thir: plate of gypsum or mica between the two mirrors. When the interposed plate belongs to a monoaxial mineral, there is seen in the second mirror a system of circular concentric colored rings intersected by a black cross (fig. 97). If the mineral is binaxial, one or two systems of elliptical colored rings appear, each intersected by a black stripe (fig. 98). In certain cases this stripe is curved, or the two systems of rings unite in a lemniscoidal form (fig. 99). When the planes of polarization are parallel, the black cross and stripe appear white .(fig. 100), showing that in this direc- tion the crystals act like singly-refract- ing minerals. Quartz, again, in close relation to its system of 'crystalliza- tion, exhibits a Circular polarization of splendid prismatic colors, which, on turning the plate, change in each point in the order of the spectrum, from red to yellow, green, and blue. In order to produce these changes, however, in some specimens the plate must- be turned to the right, in others to the left, showing a dif- ference in the Crystalline structure. Pleochroism. Closely connected with double refraction is that property of transparent minerals named pleochroism (many-colored), in consequence of which they exhibit dis- tinct colors when viewed by transmitted light in different directions. Crystals of the tesseral system do not show this property ; while in those of the other systems it ap- pears in more or less perfection ; and in the tetragonal and hexagonal minerals as dichroism (two colors), in the rhom- bic and clinohedric systems as trichroism (three colors). In most cases these changes of color are not very decided, and appear rather as different tints or shades than as dis- PHYSICAL PKOPERTIKS OF MINERALS. 9c tinct colors. The most remarkable of dichromatic minerals are the magnesian mica from Vesuvius, the tourmaline and ripidolite ; of trichromatic, the iolite, the andalusite from Brazil, the diaspore from Schemnitz, and the axinite. Change of Colors Changing Colors Iridescence. Some crystalline minerals exhibit a very lively play or change of colors from reflected light in certain Directions. It is well seen in many various hues on the cleavage-planes of Labrador felspar, and seems produced by a multitude of very thin quadrangular pores, interposed in the mineral like minute parallel lamina?. On the cleavage-planes of the hypersthene it appears copper-red, and is occasioned by numerous small brown or black laminae of some foreign O substance interposed in a parallel position between -the planes of the hypersthene. The chatoyant, or changing colors of the sun-stone, arise from scales of iron-glance simi- larly interposed. The play of color in the noble opal seems to be produced very nearly in the same manner with that in the labradorite. A similar opalescence is seen in certain minerals when cut in particular forms. In the" sapphire, cut hemispherically over the chief axis, it appears like a star with six rays ; in certain varieties of chrysoberyl and adularia it has a bluish tint ; and is also very remarkable in the cat's-eye variety of quartz. Iridescence often arises from very fine fissures, producing semicircular arches of prismatic tints, which, like the colors of thin plates in gen- eral, are referred to the interference of light. Lustre and Color. : "^ ;' * . " Though these properties admit of no precise or mathe- matical determination, they are of considerable value in 94 A POPULAR TREATISE ON GEMS. mineralogy. One highly important distinction founded on them is that of minerals of metallic and non-metallrc aspect or character. This distinction can hardly be described in words, and the student will best learn to distinguish metal- lic colors and lustre from non-metallic by observing them in nature. Transparency and opacity nearly coincide with this division, the metallic minerals being almost constantly opaque ; the non-metallic more or less transparent. Min- erals which are perfectly opaque, and show metallic color and lustre, are named metallic; those with only two of these three properties, semi-metallic or metalloid ; and those with the opposite properties non-metallic. I/ustre has reference to the intensity and quality of the reflected light, considered as 'distinct from color. Several degrees in intensity have been named, (l.) Splendent, when a mineral reflects light so perfectly as to be visible at a great distance, and lively, well-defined images are formed in its faces, as galena, rock-crystal, or calc-spar. (2.) Shining, when the reflected light is weak, and only forms indistinct and cloudy images, as heavy spar. (3.) Glisten- ing, when the reflected light is so feeble as not to be ob- servable at a greater distance than arm's length, and the- surface can no longer form an image. (4.) Glimmering, when the mineral held near the eye in full clear daylight presents only a number of small shining points, as red haematite and granular limestone. When, as in chalk, the lustre is so feeble as to be indiscernible, it is said to be dull. In regard to the kind or quality of the lustre, the follow- ing varieties are distinguished: (1.) The metallic, seen in much perfection in native metals and their compounds with sulphur, and imperfectly in glance coal. (2.) Adamantine, found in beautiful perfection in the diamond, and in some varieties of blende and carbonate of lead. (3.) Vitreous or glassy, seen in rock-crystal or common glass, or inclining PHYSICAL PROPERTIES OP MTJTERALS. 95 to adamantine in flint-glass. (4..) Resinous, when the body appears as if smeared with oil, as in pitch-stone and garnet. (5.) Pearly, like mother-of-pearl, seen in stilbite, gypsum, mica. (6.) Silky, the glimmering lustre seen on fine fibrous aggregates like amianthus. Color. This property is not in all cases of equal value as a character. Thus some minerals are naturally colored, showing in all modes of their occurrence one determinate color, which is therefore essential, and forms a characteristic of the species. This class includes the metals, pyrites, blendes, with many metallic oxides and salts. A second class of minerals are colorless, their purest forms being white, or clear like water, as ice, calc-spar, quartz, adularia, and many silicates. But these minerals are occasionally colored that is, accidentally tinged, sometimes from the chemical or mechanical admixture of some coloring sub- stance, as a metallic oxide, carbon, or particles of colored minerals ; at other times from the substitution of a colored for an uncolored isomorphous element. The colors of these minerals therefore vary indefinitely, and can never charac- terize the species, but only its varieties. Thus, quartz, calc-spar, fluor spar, gypsum, and felspar are often colored accidentally by pigments mechanically mixed ; and horn- blende, augite, garnet, and other colorless silicates, acquire green, brown, red, or black tints from the introduction of the isomorphic coloring elements. "Werner, who bestowed much attention on this portion of mineralogy, distinguished eight principal colors, white, gray, black, blue, green, yellow, red, and brown, each with several varieties or shades arising from intermixture with the other colors. He also divided them into metallic and non-metallic as follows : 96 A POPULAR TREATISE ON GEMS. METALLIC COLORS. 1. White. (1.) Silver-white, as in Icucopyrite and native silver. (2.) Tin-white'; native antimony. 2. .Gray. (1.) Lead-gray; galena or lead glance. (2.) Steel-gray; na- tive platina. 8. Black. (1.) Iron-black; magnetite. 4. Yellow. (1.) Brass-yellow; chalcopyrite. (2.) Bronze-yellow; iron pyrites. (3.) Gold-yellqw ; native gold. 5. Red. (1.) Copper-red; native copper and nickeline. NON-METALLIC COLORS. 1. White. (1.) Snow-white ; new-fallen snow, Carrara marble, and common quartz. (2.) Eeddish-white ; heavy spar. (3.) Yellowish-white; chalk. (4.) Grayish-white ; quartz. (5.) Greenish-white ; amianthus. (0.) Milk-white; skimmed milk, chalcedony. 2. Gray. (1.) Bluish-gray; limestone. (2.) Pearl-gray; porcelain jas- per, and rarely quartz.. (3.) Smoke-gray or brownish-gray; dense smoke, dark varieties of flint. (4.) Greenish-gray; clay-slate and-whet-slate. (5.) Yellowish-gray; chalcedony. (6.) Ash-gray; wood-ashes, zoisite, zircon, and slate-clay. 3. Slack. (1.) Grayish-black; basalt, Lydia'n stone, and lucullite.. (2.) Velvet-black; obsidian and schorl. (3.) Pitch-black or brownish-black; cobalt ochre, bituminous coal, and some varieties of mica. (4.) Greenish- black or raven- black; hornblende. (5.) Bluish-black; fluorspar. 4. Blue. (1.) Blackish-blue; dark varieties of azurite. (2.) Azure-blue; bright varieties of azurite and lapis lazuli. (3.) Violet- blue; amethyst and fluor spar. (4.) Lavender-blue; lithomarge and porcelain jasper. (5.) Plum-blue; spinel and fluor spar. (6.) Berlin-blue; sapphire, rock- salt, cyanite. (7.) Smalt-blue ; pale-colored smalt, gypsum. (8.) Duck- blue ; talc and corundum. (9.) Indigo-blue ; earthy-blue iron or vivianite. (10.) Sky-blue ; liroconite, some varieties of fluor spar and of blue spar. 5. Green. (1.) Verdigris-green; amazon stone and liroconite. (2.) Cel- andine-green; green earth, Siberian and Brazilian beryl. (3.) Mountain- green; beryl, aqua-marine topaz. (4.) Leek-green; common actynolite and prase. (5.) Emerald-green; emerald, and some varieties of green malachite. (6.) Apple-green; chrysoprase. (7.) Grass-green; uranite, pmaragdite, (8.) Blackish-green; augite and precious serpentine. (9.) Pistachio-green; chrysolite and epidote. (10.) Asparagus-green; the apatite or asparagus-stone from Spain and Salzburg. (11.) Olive-green ; garnet, pitch-stone, and olivine. (12.) Oil-green; olive-oil, blende, beryl. (13.) Siskin-green; uranite, and some varieties of pyromorphite. 6. Yellow. (1.) Sulphur-yellow; native sulphur. (2.) Straw-yellow; PHYSICAL PROPERTIES OP MINERALS. 97 pycnite and karpholite. (3.) "Wax-yellow; opal and wulfenite. (4.) Hon- ey-yellow; dark honey, fluor spar, and beryl. (5.) Lemon-yellow; rind of ripe lemons, orpiment. (6.) Ochre-yellow; yellow-earth and jasper. (7.) Wine-yellow ; Saxon and Brazilian topaz and fluor spar. (8.) Cream- yellow or Isabella-yellow ; bole from Strigau, and compact limestone. (9.) Orange-yellow, rind of the ripe orange, uran-ochre, and some varieties of wulfenite. 7. Red. (1.) Aurora, or morning-red ; realgar. (2.) Hyacinth-red; hya- cinth or zircon, and garnet. (3.) Tile-red ; fresh-burned bricks, porcelain- jasper, and heulandite. (.4.) Scarlet-red; light-red cinnabar. (5.) Blood- red; blood, pyrope. (6.) Flesh-red; felspar and barytes. (7.) Carmine- red; carmine, spinel, particularly in thin splinters. (8.) Cochineal-red; cinnabar and certain garnets. (9.) Crimson-red ; . oriental ruby and eryth- rine. (10.) Cclumbine-red ; precious garnet. (11.) Rose-red; diallogite and rose-quartz. (12.) Peach-blossom red ; blossoms of the peach, red cobalt-ochre. (13.) Cherry-red; spinel, kermes, and precious garnet. (14.) Brownish-red; reddle and columnar-clay ironstone. 8. JBrotcn. (1.) Reddish- brown; brown blende from the Hartz, and zircon. (2.) Clove-brown ; the clove, rock-crystal, and axinite. (3.) Hair- brown ; wood-opal and limonite. (4.) Broccoli-brown ; zircon. (5.) Chestnut-brown; Egyptian jasper. (6.) Yellowish-brown; iron flint and jasper. (7.) Pinchbeck-brown; tarnished pinchbeck, mica. (8.) Wood- brown ; mountain wood and old rotten wood. (9.) Liver-brown ; boiled liver, common jasper. (10.) Blackish-brown ; mineral pitch and brown coal. The accidentally-colored minerals sometimes present two or more colors or tints, even on a single, crystal; very re- markable examples occurring in fluor spar, apatite, sapphire, amethyst, tourmaline, and cyanite. This is still more com- mon in compound minerals, on which the colors are va- riously arranged in points, streaks, clouds, veins, stripes, bands, or in brecciated and ruin-like forms. . Some miner- als again change their color from exposure to the light, the air, or damp. Sometimes merely the surface is affected or tarnished, and then appears covered as with a thin film, producing in some minerals, as silver, arsenic, bismuth, only one color ; in others, as copper pyrites, hematite, stibine, and common coal, various or iridescent hues. Occasionally the change pervades the whole mineral, the color some- V" 5 98 A POPULAR TEEATISE ON GEMS. times becoming paler, or disappearing, as in ehrysoprase and rose-quartz ; at other times darker, as in brown spar, siderite, and rhodonite. In a few minerals a complete change of color takes place, as in the chlorophaeite of the Western Isles, which, on exposure for a few hours, passes from a transparent yellow-gre'en to black. These mutations seem generally connected with some chemical change. The tarnished colors sometimes only appear on certain faces of a crystal belonging to a peculiar form. Thus a crystal of copper pyrites (like fig. 35) has one face P' free from tar- nish ; the faces b and c, close to P', are dark blue ; the re- mainder of c, first violet, and then, close to P, gold-yellow. The color of the powder formed when a mineral is scratched by a hard body is often *different from that of the solid mass. This is named the streak, and is very characteristic of many minerals. It also often shows a peculiar lustre where the mineral is soft, as in talc and steatite. Phosphorescence, Electricity, Magnetism. Phosphorescence is the property possessed by particular minerals of producing light in certain circumstances with- out combustion or ignition. Thus some minerals appear luminous when taken into the dark after being for a time exposed to the sun's rays, or even to the ordinary daylight. Many diamonds and calcined barytes exhibit this property in a remarkable degree ; less so, arragonite, calc-spar, and chalk ; and in a still inferior degree, rock-salt, fibrous gyp- sum, and fluor spar. Many minerals, including the greater part of those thus rendered -phosphorescent by the influ- ence of the sun, also become so through heat. Thus some topazes, diamonds, and varieties of fluor spar, become lumi- nous by the heat of the hand ; other varieties of fluor spar and the phosphorite require a temperature near that of boil- PHYSICAL PEOPEETIES OF ]Sn> T ERALS. 99 ing water; while calc-spar and many silicates are only phosphorescent at from 400 to 700 Fahr. Electricity produces it in some minerals, as in green fluor spar and calcined barytes. In others it is excited when they are struck, rubbed, split, or broken ; as many varieties of zinc- blende and dolomite when scratched with a quill, pieces of quartz when rubbed on each other, and plates of mica when suddenly separated. Friction, pressure, and heat also excite electricity in minerals. To observe this property; delicate electroscopes are required, formed of a light needle, terminating at both ends in small balls, and suspended horizontally on a steel pivot by an agate cup. Such an instrument can be nega- tively electrified by touching it with a stick of sealing-wax, excited by rubbing, or positively when the wax is only brought so n^ear as to attract the needle. When the in- strument is in this state the mineral, if also rendered elec- tric by heat or friction, will attract or repel the needle ac- cording as it has acquired electricity of an opposite or similar kind ; but if the mineral is not electric, it will at- tract the needle in both conditions alike. Most precious stones become electrical from friction, and are either posi- tive or negative according as their surface is smooth or rough. Pressure even between the fingers will excite dis- tinct positive electricity in pieces of transparent double- refracting calc-spar. Topaz, arragonite, fluor spar, car- bonate of lead, quartz, and other minerals show this property. Heat or change of temperature excites electricity in many crystals, as in tourmaline, calamine, topaz, calc-spar, beryl, barytes, fluor spar, diamond, garnet, and others, which are hence said to be thermo or pyroelectric. Some acquire polar pyro-electricity, or the two electricities appear in op- posite parts of the crystal, which are named, its electric 100 A POPULAR TREATISE ON GEMS. poles. Each pole is alternately positive and negative, the one when the mineral is heating, the other when it is cool- ing. The poles that become positive during an increase of temperature are named analogue ; those that become nega- tive in the same condition, antilogue poles, as shown in this table : Temperature. -f- or rising ). or falling f Produces in analogue poles Electricity, j -j- or vitreous. 1 or resinous. -j- or rising ) or fulling j in antilogue poles j or resinous. 1 -f- or vitreous. As already noticed, many polar electric minerals are also remarkable for their hemimorphic crystal forms. The num- ber and distribution of the poles likewise vary. In many monoaxial minerals, as tourmaline and calamine, there are only two poles, one at each end of the chief a^is ; whereas boracite has eight poles corresponding to the angles of the cube. In prehnite and- topaz, again, two antilogue poles occur on the obtuse lateral edges of the prism ooP, and one analogue pole corresponding to the macrodiagonal chief section, or in the middle of the diagonal joining the obtuse edges. The power of retaining the electricity ac- quired by rubbing, for a longer time, varies in different minerals and gems ; and as the latter are all electric, this property may sometimes be used as a distinguishing char- acter as to the length of retaining the electricity. Abbe Haily found, in his experiments, that many precious stones lose their electric power after a few moments, whereas some will retain the same for twenty-four hours longer. The Brazilian topaz affected the needle, even after thirty-two hours. Magnetism, or the power to act on the magnetic needle, is very characteristic of the few minerals in which it occurs, chiefly ores of iron or nickel. It is either simple, attracting PHYSICAL PROPERTIES OF MINERALS. 101 both 'poles of the needle ; or polar, when one part attracts, and another repels the same pole. Some magnetic iron ores, or natural magnets, possess polar magnetism ; while the common varieties, meteoric iron, magnetic pyrites, precious garnet, and other minerals, are simply magnetic. Most minerals 'are only attracted by the magnet, but do not themselves attract iron. Smell, taste,. and. touch furnish a few characters of min- erals. Most have no smell, but some give out a peculiar odor when rubbed : as quartz, an empyreumatic- odor, or smell of burning ; fluor spar, of chlorine ; clay, of clay ; some limestones and marls, of bitumen, or a fetid odor. Aluminous minerals acquire a smell when breathed on. Other odors caused by heat, and often highly character- istic, are noticed under tests by the blo\vpipe. Taste is produced by all the salts soluble in water. Some are saline, like common salt ; sweetish astringent, like alum ; astringent like blue vitriol ; bitter, like epsom salts; cooling, like saltpetre; pungent, like sal-ammoniac; alkaline, like soda ; acid or sour, like sassoline, &c. Touch. Some minerals are distinguished by a greasy feeling, like talc ; others feel meagre, like clay ; others cold. The last character readily distinguishes true gems from their imitations in glass.. 102 A POPULAR TREATISE ON GEMS. CHAPTER III. CHEMICAL PROPERTIES OF MINERALS. THE consideration of the chemical nature of minerals, that is, of the elements that enter into their composition, of the manner in which these elements combine, and the variations in proportion which they may undergo without destroying the.identity of the species, forms an important branch of mineralogical science. The. methods of detect- ing the different elements, and the characters which are thus furnished for the discrimination of minerals, are also of much value. This is especially true of the metallic ores and other .substances, sought not as objects of curiosity, but for their economic qualities. Composition of Minerals. At present about sixty elements, or substances which have not been decomposed, are known. These are divided into metallic and non-metallic, a distinction of importance in mineralogy, though not always to be carried out with precision. The non-metallic elements are rarely of semi- metallic aspect, and are bad conductors of heat and elec- tricity. Some are commonly gaseous oxygen, hydrogen, nitrogen, chlorine, and fluorine ; one fluid bromine ; the others solid carbon, phosphorus, 'sulphur, boron, selenium, and iodine. The metallic elements are, except mercury, solid at usual temperatures, have generally a metallic aspect, and are good conductors of heat and electricity. They are divided into light and heavy metals, the former with a CHEMICAL PROPERTIES OF MINERALS. 103 specific gravity under 5, and a great affinity for oxygen, and again distinguished as either alkali-metals, potassium (or kalium), sodium (or natrium), lithium, barium, stron- tium, and calcium ; or earth-metals, magnesium, lanthani- um, yttrium, glucinum, aluminium, zirconium, silicium. The heavy metals, with a specific gravity above 5, are divided into noble, which can be reduced or separated, from- oxygen, by heat alone ; and ignoble, whose affinity for oxygen renders them irreducible without other agents. Some of the latter are brittle and difficultly fusible, tho- rium, titanium, tantalium (columbium), tungsten (wolfra- mium), molybdenum, vanadium, chromium, uranium, man- ganese, and cerium ; others are brittle and easily fusible or volatile arsenic, antimony, tellurium, and bismuth; and others malleable zinc, cadmium, tin, lead, iron, cobalt, nickel, and copper. The noble metals are, quicksilver, silver, gold, platinum, palladium, rhodium, iridium, and osmium. All the chemical combinations observed in the mineral kingdom follow the law of definite proportions; that is, two elements always combine either in the same proportion, or so that the quantity of the one is multiplied by two, three, four, or some other definite number seldom very large. As the same law prevails throughout the whole range of elements, by assuming any one, usually hydrogen or oxygen, as unity or 1, and determining froqfc experiment the simple proportion in which the others combine with it, a series of numbers is obtained which als"o expresses the proportions in which all these elements combine with each other. These numbers, therefore, mark the combining proportions or equivalents, as they are named, of the ele- ments. They are also named atomic weights, on the sup- position that matter consists of definite atoms, and that its combinations consist of one atom (or sometimes two atoms) 104 A POPULAR TREATISE ON GEMS. of one substance, with one, two, three, or more atoms of another. This theory is not free from difficulties, but the language is often convenient. To designate the elements, chemists generally employ the first letter or letters of their Latin names. These signs also .indicate one atom or equivalent of the element. Thus, O means oxygen in the proportion of one atom ; H, hydrogen in the same propor- tion ; N", an atom of nitrogen ; Na, an equivalent propor- tion of natrium or sodium. These signs and the equivalent weights are given in the table on next page, in one column of which hydrogen is taken as unity, in the other oxygen. Thte elements are arranged according to Berzelius, begin- ning with the most electro-positive, and ending with the most electro-negative. All these elements occur in minerals, but not more than twenty are common, and only about twelve abundant. They are also very rare in their simple or uncombined state ; only 'carbon in the diamond and graphite, sulphur, and about a dozen of the native metals, being thus known. More frequently minerals consist of two or more elements combined in accordance with those laws which prevail in inorganic compounds. The most important of these laws is that the combinations are binary; that is, that the ele- ments unite in pairs, which may again unite either with another compound of two, or with a single element. Inor- ganic compdtnds also are generally distinguished from or- ganic by their greater simplicity. CHEMICAL PROPERTIES OF MINERALS. 105 TABLE I. Elements arranged in Electro- Chemical order. Name. Sign. Atomic Weight. Name. Sign. Atomic Weight H=l 0=100. H=l O=100. Potassium .... Sodiam. ... K Na Li NH3 Ba Sr Ca M g Fe Ni Co Zn Cd Sn Pb Bi Cu ?* Pi Rh Ru Ir Pt 03 Au H c { 39-2 23-2 7 17 68-6 44 20 12-5 32 28 29 30 32-2 56 59 104 208 31-7 100 108 53-3 52 99 99 99 168 1 15 22'2 6 488-85 290-9 86-9 856-88 547-28 251-5 ' 154-5 402-51 350-53 362-8 375 406-59 696-76 735-29 1294-5 *2600 395-69 1250 1349-66 665*84 651-4 1283-26 1233-26 1244-21 *2458-83 *12-48 tl87-5 J277-31 75-415 Glucinum 'Aluminium . . . .Zirconium [Thorium Q Al Zr Th Ce La D u Mn B Ti Ta Nb Pp W Mo V Cr Te Sb As P N Se S O I Br Ci F 7 13-7 22-5 59-6 46 36? 60 28 11 25 185 92* 46 66-6 26-3 64 122 75 31 14 40 16 8 126 78-4 36 18-7 86-5 1 *342-33 *S40'4 744-90 575 746-86 345-89 136-2 303-63 1153-715 .... 1150 : 78 575-83 855-8 328-59 802-12 1529-2 *940-08 *392-28 *175-06 494-58 200-75 100 *1586 *999-62 *443-28 *233'SO Lithium Ammonium... Barium Cerium Strontium jLanthanium.. . iDidjrmium ... I Uranium (Manganese ... Boron Calcium. Magnesium . . . Yttrium Iron Nickel Titanium. . Cobalt Tantalium. ; Niobium . 'Pelopium? jWolframium.. Molybdenum. i Vanadium Chromium... . 1 Zinc Cadmium Tin. Lead Bismuth Copper . . Mercury Silver.. Palladium Rhodium . . . i Antimony Arsenic . Phosphorus... Nitrogen Ruthenium Selenium > Sulphur. . Platinum . Osmium Oxvgen Gold. i Iodine Hydrogen Siliciuni Bromine . Chlorine Carbon . . . ! * Double atoms, t L. Gmelin, who considers silica as composed of one atom base and two oxygen. % Berzelius. The above list includes ammonium, usually considered -a compound body, and omits the two new metals, erbium .and" terbium. The following principles are observed in designating the combinations of these elementary substances : For those of 5- 106 A POPULAR TEEATISE ON GEMS. the first order the signs of the two components are con- joined, and the number of atoms or equivalents of each ex- pressed by a number following the sign like an algebraic exponent. Thus, SO, SO 2 , SO 3 , are the combinations of one atom sulphur with one, two, and three atoms of oxygen ; FeS, FeS 2 , of one atom of iron with one or two of sulphur. But as combinations with oxygen and sulphur are very numerous in the mineral kingdom, Berzelius, to whom science is indebted for this system of signs, marks the atoms of oxygen by dots over the, sign of the other element, and those of sulphur by an accent ; the above compounds being then designated thus S, S, S, and Fe', Fe". In some cases two atoms of a base combine with three or five of oxygen or sulphur, as APO 3 , Fe 2 S 3 . In such cases Berzelius marks the double atom by a line drawn through the sign of the single atom ; thus, Al is two atoms aluminium with three of oxygen, or alumina ; -On, two of copper with one of oxy- gen, or oxide of copper. Where a number is prefixed to the sign like a coefficient in algebra, it includes both elements of the combination ; thus H is one atom water, 2 H two ; CaC is one atom carbonate of lime, 2 CaC two atoms, includ- ing, of course, two of calcium, two of carbon, and six of oxygen. The most common and important binary compounds are those with oxygen, contained in the following table, with their signs, atomic numbers, and amount of oxygen in 100 parts. The more electro-negative are named acids, which are often soluble in water, and then render blue vegetable colors red. The more electro-positive are named oxides or bases, and show great affinity or attractive power for the former. The most powerful are the alkaline bases, which are colorless and soluble in water ; less powerful are the earths, also colorless, but insoluble in water : TABLE II. Binary Compounds with Oxygen. 107 Name. Sign. Atomic Weight Oxyg. in 100 par ts. o 3 f PH ^ II < 5 "o 1 3 _ r3 o | ^5 .3 p rt 00 1 "e3 ^0 2 3 ^0 d 1 .22 t3 KH O fc H=l. O=l 00. Alumina Ai Sb ft *Sb As '\* Ba Bi B* d Co fcb C'r bV Co 60 da o" Ke JPe Fe-f-Fe Pb Ca i.r Mg Mn VIM M..+MII Mo Ni '*' >V K Si Si' Na S'r 8* ta Th Sn Ti W ir u V H Y Zn Zr *Zr 51-4 146 154 162 99 115 766 232 34 8 22 54 116 76-6 50 3 38 714 39-7 38 36 80 116 i!2 28 15 21 36 80 116 70 37 54 71 47-2 31 46-2 31-2 52 4Q 209 67-6 75 41 116 68 144 92 9 40 402 304 642 33 1829-2 1929-2 2029-2 1240-08 1440-08 95688 2900-00 436-20 2750 674-72 1449-39 956-78 628-39 475 891 -39 495-69 490-05 450-527 1001-054 1451-581 1394-50 351 -489 186-9 254-50 44589 991-77 1437-66 875-83 4628 675-06 892-28 588-856 387-5 577-31 390-90 647-29 500-75 2607-43 844-90 935-29 503-68 1450-78 84284 1792-72 1155 84 112-48 502-51 506-59 114-2 46-70 16-40 20-73 24-64 34-72 10-45 10-34 68-78 72-73 1482' 2070 31-35 47 74 21-05 11 12 2017 6326 22-19 29-97 26-08 7-17 v28-45 5350 39-30 2243 30-25 26-34 34-28 21-60 7407 5604 1698 51-61 51 96 25-58 1545 59-91 11-51 13 34 21-38 39-71 20-67 1333 10 13 26 19 88-89 19-90 1974 26-37 Antimony oxide Antimoniousacid Antimonic acid Arsenious acid Arsenic acid Bary ta Bismuth- peroxide Boracic acid Carbonic acid Cerium protoxide " peroxide Chromium oxide Chromic acid Cobalt protoxide. Copper suboxide (red) ' ' protoxide (black) . . Glucina Iron protoxide " peroxide (red) " pro to- peroxide (black) Lead protoxide Magnesia Manganese protoxide.. . " peroxide. 4i proto-perox. (red) Molybdio acid Nickel protoxide. Nitric acid Phosphoric acid Potassa Silica (Gmelin) " (Berzelius). Soda Strontia Sulphuric acid Tantalic acid . . Thorina Tin peroxide Titanic acid Tungstic acid . ... Uranium protoxide " peroxide Vanadic acid . ... Water.. .... Yttria Zinc oxide Zirconia 108 A POPULAR TREATISE ON GEMS. Similar to the compounds of oxygen are those with sul- phur, usually named sulphurets, and considered analogous to the oxidized bases. A few of more electro-negative character, resembling acids, have been distinguished as sul- phides. Some other compounds have been named haloid gaits, and consist of certain electro-negative elements, com- bined with electro-positive ones, as bases. Many of these combinations occur as independent species in the mineral kingdom, especially those with, oxygen and sulphur. Thus the most abundant of all minerals, quartz, is an oxide, and corundum is of similar nature. Many oxides of the heavy metals, as of iron, tin, copper, and anti- mony ; and some super-oxides, as of lead and manganese (pyrolusite), are very common. Compounds with sulphur also abound, either as sulphides, with the character of acids, like realgar, orpiment, and stibine ; or as sulphurets, resembling bases, like galena, argentite, and pyrite. Less frequent are haloid salts, with chlorine and fluorine, as common salt and fluor spar; and still rarer those with iodine and bromine. On the other hand, metallic alloys, or combinations of electro-negative with electro-positive metals, are far from uncommon, especially those with arsenic, tellurium, or antimony. Combinations of these binary compounds with each other are still more common, the greater number of minerals being composed of an acid and base. By far the greater number are oxygen-salts, distinguished by giving to the acid the termination ate ; thu-s sulphate of .lead, silicate of lime, and in like manner numerous carbonates, phosphates, arseniates, aluminates. The sulphur-salts (two metals com- bined with sulphur, and these again combined with each other) are next in number, and perform a most important part in the mineral kingdom. The hydrates, or combina- tions of an oxide with water, are also common, and much CHEMICAL PROPERTIES OF MINERALS. 109 resemble the oxygen salts, the water sometimes acting as an electro-positive, at other times as an electro-negative element. Combinations of a higher order are likewise common, especially the double salts, or the union of two salts into a new body ; and even these again w r ith water, as alum and many hydrous silicates. The chemical formulas for these compound salts are formed by writing the signs of the simple salts with the sign of addition between them : thus Ca C-f-'Mg C, i. e., carbonate of lime and carbonate of magnesia, or brown spar ; Al Si 3 + K Si 3 , or orthoclase ; 3 Na F + Al 2 F 3 ,* or cryolite, composed of three compound atoms of fluorine and sodium united to one compound atom, consisting of three of fluorine and two of aluminium. Influence of the Chemical Composition on the External Characters of Minerals. That the characters of the compound must in some way or other depend on those of its component elements, seems, as a general proposition, to admit of no doubt. Hence it might be supposed possible, from a knowledge of the com- position of a mineral, to draw conclusions in reference to its form and other properties; but practically this. has not yet been effected'. The distinction between the mineral- izing and mineralizable, or the forming and formed, ele- ments, lies at the foundation .of all such inquiries. Certain elements hi a compound apparently exert more than an equal share of influence in determining its physical prop- erties. Thus the more important non-metallic elements, as oxygen, sulphur, chlorine, fluorine, are remarkable for the influence they exert on the character of the compound. The sulphurets, for example, have more similarity among themselves than the various compounds of one and the same metal with the non-metallic bodies. Still more gen- 110 A PO?ULAK TKEATISE ON GEMS. erally it would appear that the electro-negative element in the compound is the most influential, or exerts the greatest degree of active forming power. After the non-metallic elements the brittle, easily fusible metals rank next in power; then the ductile ignoble metals; then the noble metals ; then the brittle, difficultly fusible ; and last of all, the metals of the earths and alkalies. It is sometimes stated that each particular substance can crystallize only in one particular form or series of forms. This is, however, only partially true; and sulphur, for in- stance, which usually crystallizes in the rhombic system, when melted may form monoclinohedric crystals. This property is named dimorphism ; and hence the same chem- ical substance may form two, or even more distinct bodies or mineral species. Thus carbon in one form is the dia- mond, in another graphite ; carbonate of lime appears as calc-spar or arragonite ; the bisulphuret of iron, as pyrite and marcasite. An example of trimorphism occurs in the titanic acid, forming the three distinct species, anatase, rutile, and brookite. Even the . temperature at which a substance crystallizes -influences its forms, and so far its composition, as seen in 'an-agonite, Glauber salt, natron, and borax. Still more important is the doctrine of isomorphism, des- ignating the fact that two or more simple or compound substances crystallize in one and the same form ; or often in forms which, though not identical, yet approximate very closely. This similarity of form is generally combined with a similarity in other physical properties. Among minerals that crystallize in the tesseral form, isomorphism is of course common and perfect, there being no diversity in the dimen- sions of the primary form ; but for this very reason it is of less interest. It is of more importance among mono-axial crystals, the various series of which are separated from each CHEMICAL PKOPERTIES OF MINERALS. Ill other by differences in the proportion of the primary form In these, perfect identity is seldom observed, but only very great similarity. The more important isomorphic substances are the fol- lowing : I. Simple substances : (l.) Fluorine and chlorine. (2.) Sulphur and selenium. (3.) Arsenic, antimony, tellurium. (4.) Cobalt, iron, nickel. (5.) Copper, silver, quicksilver, gold (?). II. Combinations with oxygen : (1.) Of the formula B. (a.) Lime, magnesia, protoxide of iron, protoxide of manganese, oxide of zinc, oxide of nickel, oxide of cobalt, potassa, soda. (b.) Lime, baryta, strontia, lead-oxide. (2.) Of the formula S. (a.) Alumina, peroxide of iron, peroxide of manga- nese, oxide of chromium. (b.) Antimony oxide, arsenious acid. (3.) Formula R. Tin-oxide, titanium-oxide. (4.) Formula R. Phosphoric acid, arsenic acid. (5.) Formula R. (a.) Sulphuric acid,.selenic acid, chromic acid, man- ganese acid. (b.) Tungstic acid, molybdic acid. HI. Combinations with sulphur : (1.) Formula R f . Sulphuret of iron Fe', and sulphu- ret of zinc Zn'. (2.) Formula ft'". Sulphuret of^antimony Sb' 1 ', and sulphuret of Arsenic As'". (3.) Formula -R'. Sulphuret of copper -0u', and sul- phuret of silver Ag'. 112 A POPULAR TREATISE ON GEMS. These substances are named vicarious, from the singular property that in chemical compounds they can mutually replace each other in indefinite proportions, and very often without producing any important change in the form or other physical properties. But there are numerous in- stances among the silicates, where the mutual replacement of the isomorphic bodies, especially when the oxides of the heavy metals come in the room of the earths and alkalies, exerts a most essential influence on the external aspect oi the species, particularly in regard to color, specific gravity, and transparency. The varieties of hornblende, augite, garnet, epidote, and many other minerals, are remarkable proofs of this influence. This intermixture *of isomorphic elements confers many valuable properties on minerals, and .to it this department of nature owes much of its variety and beauty. Without the occasional presence of the coloring substances, especially the oxides . of iron and manganese, the non-metallic combinations would have exhibited a very monotonous aspect. It is also remarkable, that in some silicates the substitution of a certain portion of the metallic oxides for the earthy bases seems to be almost a regular occurrence; while in others, as the felspars and zeolites, this rarely happens. This fact is of very great economic importance, as drawing attention to important elements often combined with others of less value. Thus iron oxide and chrome oxide, sulphuret of copper and sulphuret of silver, nickel and cobalt, may be looked for in connection. The general chemical formula for such compounds is formed by writing R (= radicle or basis) for the whole isomorphic elements; and in special instances to place their signs either one below the other, connected by a bracket, or, as is more convenient, to inclose them in brackets one after the other, separated by a comma. Thus the general sign for the garnet is R 3 Si 2 +R Si, which, w T hen fully expressed. CHEMICAL PROPERTIES OF MINERALS. 113 ;-, becomes Fe 1 1 Si'+^- [ Si; or(Ca ! ,Fe 3 ,Mn 3 )Si'+(Al,e)Si, fin'} and the mineral forms many varieties, as the one or other element predominates. Chemical Reaction of Minerals. The object pf the chemical examination of minerals is the discovery of those elementary substances of which the j consist. This examination is named qualitative when the nature of the elements alone, quantitative when also their relative amount, is sought to be determined. Mineralogists are in general content with such an examination as will discover the more important elements, and which can be carried on with a simple apparatus, and small quantities of the substance investigated. The indications thus furnished of the true character of the mineral are, however, frequently of high importance. Two methods of testing minerals are employed, the one by heat chiefly applied through the blow- pipe, the second by acids and other reagents in solution. Use of the Blowpipe- The blowpipe in its simplest form is merely a conical tube of brass or othei* metal, curved round at the smaller extremity, and terminating in a minute circular aperture not larger than a fine needle. Other forms have been proposed, one of the" most useful being a cone of tin, open for the application of the mouth at the smaller end, and with a brass or platina beak projecting from the side near the other or broad end. With this instrument a stream of air is conveyed from the mouth to the flame of a lamp or candle, so that this can be turned aside, concentrated, and 114 A POPULAR TREATISE ON GEMS. directed upon any small object. The flame thus acted on consists of two parts the one nearest the beak of the blow- pipe forming a blue obscure cone, the other external to this being of a shining yellow or reddish-yellow color. The blue cone consists of the inflammable gases not yet fully incandescent, and the greatest heat is just beyond its point, where this is fully effected. The blue flame still needs oxygen for its support, and consequently tends to withdraw it from any body placed within its influence, and is named the reducing flame. At the extremity of the yellow cone, on the other hand, the whole gases being consumed and the external air having free access, bodies are combined with oxygen, and this part is named the oxidating flame. Their action being so distinct, it is of great importance for the student to learn to distinguish accurately these two portions of the flame. This is best done by experimenting on a piece of metallic tin, which can only be kept pure in a good reducing flame, and acquires a white crust when acted on by the oxidating flame. The portion of the mineral to be examined should not be larger than a peppercorn, or a fine splinter a line or two long. It is supported in the flame either by a pair of fine pincers pointed with platinum, or on slips of platinum-foil, or on charcoal. Platinum is best for the siliceous minerals, whereas for metallic substances charcoal must be employed. For this purpose solid uniform pieces are chosen, and a small cavity formed in the surface in which the mineral to be tested can be deposited. In examining a mineral by heat, it should be first tested alone, and then with various reagents. When placed alone in a matrass or tube of glass closed at one end, and heated over a spirit-lamp, water or other volatile ingredients, mer- cury, arsenic, tellurium, often sulphur, may readily be de- tected, being deposited in the cooler part of the tube, or, CHEMICAL PROPERTIES OF MINERALS. 115 like fluorine, acting on the glass. It may next be tried in an open tube of glass, through which a more or less strong current of air passes according to the inclination at which the tube is held, so that volatile oxides or acids may be formed ; and in this way the chief combinations of sulphur, selenium, tellurium, and arsenic are detected. On char- coal, in the reducing flame, arsenic, and in the oxidating flame, selenium or sulphur, are shown by their peculiar odor ; antimony, zinc, lead, and bismuth leave a mark or colored ring on the charcoal ; and other oxides and sul- phurets are reduced to the pure metal. On charcoal or in the platinum pincers the fusibility of minerals is tested, and some other phenomena should be observed as whether they intumesce (bubble up), effervesce, give out fumes, be- come shining, or impart a color to the flame. The color is seen when the assay is heated at the point of the inner flame, and is Reddish-yellow, from soda and its'salts ; 9 Violet, from potash and most of its salts ; Red, from litliia, strontia, and lime ; Green, from baryta, phosphoric acid, boracic acid, molybdic acid, copper oxide, and tellurium oxide ;. Blue, from chloride of copper, bromide of copper, selenium, arsenic, antimony, and lead. The fusibility, or ease with which a mineral is melted, should also be observed; and to render this character more precise, Yon Kobell has proposed this scale: (l.) Anti- mony glance, which melts readily in the mere candle flame ; (2.) Xatrolite, which in fine needles also melts in the candle flame, and in large pieces readily before the blowpipe ; (3.) Almandine (garnet from Zillerthal), which does not melt in the candle flame even in fine splinters, but in large pieces before the blowpipe ; (4.) Strahlstein (hornblende from Zillerthal) melts with some difficulty, but still more readily than (5.) Orthoclase (or adularia felspar) ; and (6.) Bron- 116 A POPULAR TREATISE ON GEMS. zite or diallage, of which only the finest fibres can be rounded by the blowpipe. In employing this scale, fine fragments of the test minerals and of that to be tried, and nearly of equal size, should be exposed at the same time to the flame. A more common mode of expressing fusibility is to state whether it is observable in large or small grains, in fine splinters, or only on sharp angles. The result or product of fusion also yields important characters, being sometimes a glass, clear, opaque, or colored ; at other times an enamel, or a mere slag. The most important reagents for testing minerals with the blowpipe are the following: (1.) Soda (the carbonate), acting as a flux for quartz and many silicates, and especially for reducing the metallic oxides. For the' latter purpose, the assay (or mineral to be tried) is reduced to powder, kneaded up with moist soda into a small ball, and placed in a cavity of the charcoal. Very often both the soda and assa^ sink into the charcoal, 'but by continuing the opera- tion they either again appear on the surface, or, when it is completed, the charcoal containing the mass is finely pounded and washed away with water, when the reduced metal is found in the bottom of the vessel. (2.) Borax (biborate of soda) serves as a flux for many minerals, which are best, fused in- small splinters on platina wire. The borax when first exposed to the flame swells up or intumesces greatly, and it should therefore be first melted into a small bead, in which the assay is placed. During the process the student should observe whether the assay melts easily or difficultly, with or without effervescence, what color it .imparts to the product both when warm and when cold, and also the effect both of the oxidating and reducing flames. (3.) Microcos- mic salt, or salt of phosphorus (phosphate of soda and am- monia), is specially important as a test for metallic oxides, which exhibit far more decided colors with it than with CHEMICAL PROPERTIES OP MINERALS. 117 borax. It is also a useful reagent for many silicates, whose silica is separated from the base and feraains undissolved in the melted salt. (4.) Solution of cobalt (nitrate of co- balt dissolved in water), or dry oxalate of cobalt, serve as tests of alumina, magnesia, and zinc oxide. In examining minerals in th*e moist way, the first point to be considered is their solubility, of which three .degrees may be noted : (!) minerals soluble in water ; (2) minerals soluble in hydrochloric or nitric acid; and (3) those un- affected by any of these fluids. The minerals soluble in water are either acids (almost only the boracic acid or sas- solin and the arsenious acid), or oxygen or haloid salts. These are easily tested, one part of the solution being em- ployed to find the electro-positive element or basis, the other the electro-negative or acid. Minerals insoluble in water may next be tested with the above acids; the nitric acid being preferable when it is probable, from the aspect of the mineral or its conduct be- fore the blowpipe, that it contains an alloy, a sulphuret, or arseniate of some metal. In this manner the carbonic, phosphoric, arsenic, and chromic acid salts, many hydrous and anhydrous silicates, many sulphurets, arseniates, and other metallic compounds, are* dissolved, so that further tests may be employed. The minerals insoluble either in water or these acids are" sulphur, graphite, cinnabar, some metallic oxides, some sulphates, and compounds with chlorine and fluorine, and especially quartz, and various silicates. For many of these no test is required, or those furnished by the blowpipe are sufficient. The silicates and others may be fused with four times their weight of anhydrous carbonate of soda when they are rendered soluble, so that further tests may be ap- plied. 118 A POPULAR TREATISE ON GEMS. Chemical Reaction of the, more Important Element*. It is not intended in this place to describe the chemical nature of the elementary substances, and still less to enu- merate the whole of those marks by which the chemist can * detect their presence. Our object is limited principally to the conduct of minerals before the blowpipe, and to a few simple tests by which their more imp'ortant constituents may be discovered by the student. I. NON-METALLIC ELEMENTS, AND THEIR COMBINATIONS WITH OXYGEN. Nitric Acid. Most of its salts detonate when heated on charcoal. In the closed tube they form nitrous acid> easily known by its orange color and smell ; a test more clearly exhibited when the salt is mixed with copper filings and treated with concentrated sulphuric acid. When to the solution of a nitrate, a fourth part of sulphuric acid, is added, and a fragment of green vitriol placed in it, the surround- ing fluid becomes of a dark-brown color. Sulphur and its compounds, in .the glass tube or on char- coal, form sulphurous acid," easily known by its smell. The minutest amount of sulphur or sulphuric acid may be de- tected by melting the pulverized assay with two parts soda and one part borax, and placing the bead moistened with water on a plate of clean silver, which is then stained brown or black. Solutions of sulphuric acid give with chloride of barium a heavy white precipitate, insoluble in acids. Phosphoric Acid. Most combinations with this acid tinge the blowpipe flame green, especially if previously moistened with sulphuric acid. The experiment must be performed in the dark,, when even three per cent, of the acid may be detected. If the assay is melted with six parts CHEMICAL PROPERTIES OF MINERALS. 119 of soda, digested in water, filtered, and neutralized with acetic acid, the solution forms an orange-yellow layer round a crystal of nitrate of silver. This solution, with muriate of magnesia, forms a white crystalline precipitate. Selenium and Setenic Add are readily detected by the strong smell of decayed horse-radish, and leave a gray de- posit with a metallic lustre on the charcoal. Chlorine and Hs salts. When oxide of copper is melted with salt of phosphorus into a very dark-green bead, and an assay containing chlorine fused with this, the flame is tinged of a beautiful reddish-blue color, till all the chlorine is driven off. If very little chlorine is present, the assay is dissolved in nitric acid (if not soluble it must first be melted with soda on platinum wire), and the diluted solution gives, with nitrate of silver, a precipitate of chloride of silver, which is first white, but on exposure to the light becomes gradually brown, and at length black. Iodine and its salts, treated like chlorine, impart a very beautiful bright-green color to the flame ; and heated in the closed tube with sulphate of potash, yield violet-colored vapors. In solution it gives, with nitrate of silver, a pre- cipitate similar to chlorine, but which -is very difficultly soluble in ammonia. Its surest test is the blue color it im- parts to starch, best seen, by pouring concentrated sul- phuric acid over the mineral in a test tube which has a piece of paper or cotton covered with moist starch over its mouth. Bromine and its salts, treated in the same manner with salt of phosphorus and oxide of copper, color the blowpipe flame greenish-blue. In the closed tube with nitrate of potassa they yield bromine vapors, known by their yellow color and peculiar disagreeable smell. Treated with "sul- phuric acid, bromine in a few hours colors starch pome- granate-yellow. 120 A POPULAR TREATISE ON GEMS. Fluorine is shown by heating the assay with sulphate of potassa, in a closed tube with a .strip of logwood-paper in the open end. The paper becomes straw-yellow, and the glass is corroded. Another test is to heat the pulverized mineral with concentrated sulphuric acid in a shallow dish of platinum (or lead), over which a plate of glass covered with a coat of wax, through which lines have, been drawn with a piece of sharp-pointed wood, is placed. If fluorine is present, the glass is etched where exposed. JBoracic Acid. The mineral alone, or moistened with sulphuric acid, when melting, colors the flame momentarily green. If the assay be heated with sulphuric acid, and alcohol added and set on fire, the flame is colored green from the vapors of the boracic acid. Carbon, pulverized and heated with saltpetre, detonates, leaving carbonate of potassa. Carbonic acid is not easily discovered with the blowpipe, but the minerals containing it effervesce in hydrochloric acid, and the colorless gas that escapes renders litmus-paper red. In solution it forms a precipitate with lime-water, which is again dissolved with effervescence in acids. Silica, before the blowpipe, alone is unchanged ; is very slowly acted on by borax, very little by salt of phosphorus, but with soda melts entirely with a brisk effervescence into a clear glass. The silicates are decomposed by salt of phosphorus, the silica being left in the bead as a powder or a skeleton. Most of them melt with soda to a trans- parent glass. .Some silicates are dissolved in hydrochloric acid, and this the more readily the more powerful the basis, the less proportion of silica, and the greater the amount of water they contain. Sometimes the acid only extracts the basis, leaving the silica as a powder or jelly ; or the silica too is dissolved, and only gelatinizes on evapo- ration. The insoluble silicates may be first melted with CHEMICAL PROPERTIES OF MINERALS. 121 some carbonate of an alkali*, when the solution gelatinizes, and finally leaves a dry residuum, of which the part insolu- ble in warm hydrochloric acid has all the properties of silica. n. THE ALKALIES AXD EARTHS. Ammonia, heated with soda in a closed tube, is readily known by its smell. Its salts, heated with solution of potassa, also yield the vapor, known from its smell, its action on turmeric-paper, and the white fumes that rise from a glass tube dipped in hydrochloric acid held over it. Soda, imparts a reddish-yellow color to the external flame when the assay is fused or kept at a strong red heat. In solution it yields no precipitate with chloride of plati- num or sulphate of alumina. Lithia is best recognized by the beautiful carmine-red color it imparts to the flame during the fusion of a mineral containing it in considerable amount. Where the propor- tion is small, the color appears if the assay be mixed with 1 part fluor spar and 1^ parts sulphate of potassa. In concentrated solutions it forms a precipitate with the phos- phate and carbonate of soda, but none with bichloride ol platinum, sulphate of alumina, or acetic acid. Potassa gives a violet color to the external cone,' when th^assay is heated at the extremity of the oxidating flame. The presence of lithia or soda, however, disturbs this re- .action. It may still be discovered by melting the assay in borax glass colored brown by nickel oxide, which ' is changed to blue by the potassa. In concentrated solutions of potassa, the bichloride of platinum gives a citron-yellow precipitate ; acetic acid, a white granular precipitate ; and sulphate of alumina, after some time, a deposit of alum-' crystals. Baryta. The carbonate of this earth melts easily to a 6 122 A POPULAR TREATISE ON GEMS. clear glass, milk-white when cold; the sulphate is very difficultly fusible. Both strongly heated at the point of the blue flame impart a green tinge to the outer flame. When combined with silica it cannot be well discovered by the blowpipe. In solution, salts of baryta yield, with sul- phuric acid or solution of sulphate of lime, immediately a fine white precipitate insoluble in acids or alkalies. Strontia, the carbonate, even in thin plates, only melts on the edges, and forms cauliflower-like projections of dazzling brightness ; the sulphate melts easily in the oxi- dating flame, and in the reducing flame is changed into sulphuret of strontium, which, dissolved in hydrochloric acid, and evaporated to dryness, gives a fine carmine-red color to the flame of alcohol. Strontia in solution gives a precipitate with sulphuric- acid, or with sulphate of lime, but not immediately. Lime. The carbonate is rendered caustic by heat, when it has alkaline properties, and readily absorbs water. The sulphate in the reducing flame changes to the sulphuret of calcium, which is also alkaline. Sulphuric acid precipi- tates lime only from very concentrated solutions; oxalic acid even from very weak ones ; and silico-hydrofluoric acid not at all. As baryta and strontia also form precipitates with the first two reagents, they must previously be sepa- rated by sulphate of potassa. Chloride of calcium tinges the flame of alcohol yellowish-red. Magnesia, alone, or as a hydrate, a carbonate, and in some other combinations, when ignited with solution of cobalt, or the oxalate of cobalt, assumes a light-red tint. It is not precipitated from a solution either by sulphuric acid, oxalic acid, or silico-hydrofluoric acid ; but phosphoric acid, with ammonia, throws down a white crystalline pre- cipitate of phosphate of ammonia and magnesia. Alumina alone is infusible. In many combinations, when CHEMICAL PBOPERTTES OF MINERALS. 123 ignited with solution of cobalt, it assumes a fine blue color. It is thrown down by potassa or soda as a white volumin- ous precipitate, which in excess of the alkali is easily and completely soluble, but is again precipitated by muriate of ammonia. Carbonate of ammonia also produces a precipi- tate which is not soluble in excess. Glucina, Yttria, Zirconia, and Thorina are not prop- erly distinguished by blowpipe tests, though the minerals in which they occur are well marked in this way. In solution, glucina acts with potassa like alumina ; but the precipitate with carbonate of ammonia . is again soluble, with excess of the alkali, and the two earths may thus be separated. Yttria is precipitated by potassa, but is not again dissolved by excess of the alkali. With carbonate of ammonia it acts like glucina. It must be observed, however, that the substance formerly named yttria is now considered a mixture of this earth with the oxides of er- bium, terbium, and lanthanium. Zirconia acts with potassa like yttria, and with carbonate of ammonia like glucina. Concentrated sulphate of potassa throws down a double salt of zirconia and potassa, which is very little soluble in pure water. III. THE METALS. Arsenic and its sulphuret on cha/coal yield fumes, with a smell like garlic, and sublime in the closed tube. The greater number of alloys- of arsenic in the reducing flame leave a white deposit on . the charcoal ; or, where it is in larger proportion, give out grayish-white fumes with a smell of garlic. Some alloys 'also yield metallic arsenic in the closed tube. In the open tube all of them yield ar.se- nious acid, and those containing sulphur also sulphurous fumes. Many arsenic acid salts emit evident odors of arsenic when heated on charcoal with soda ; and some sub- 124 A POPULAR TREATISE ON GEMS. lime metallic arsenic when heated with pulverized charcoal in the closed tube. Antimony melts easily on charcoal, emitting dense white fumes, and leaving a ring of white crystalline oxide on the support. In the closed tube it does not sublime, but burns in the open tube with white smoke, leaving a sublimate on the glass, which is easily driven from place to place by heat. Most of its compounds, with sulphur or "with the other metals, show similar reaction. Antimony oxide on char- coal melts easily, fumes, and is reduced, coloring the flame pale greenish-blue.. Bismuth melts easily, fumes, and leaves a yellow oxide on the charcoal. In the closed tube it does not sublime, and in the open tube scarcely fumes, but is surrounded by the fused oxide, dark-brown when warm, and bright-yellow when cold. Its oxides are easily reduced. A great addi- tion of water produces a white precipitate from its solution in nitric acid. . Tellurium fumes on charcoal, and becomes surrounded by a white mark with a reddish border, which, when the reducing flame is turned on it, disappears with a bluish- green light. In the closed tube tellurium gives a subli- mate of the gray metal ; and in the open tube produces copious fumes, and a white powder which can be melted into small clear drops. . Mercury in all its combinations is volatile, and yields a metallic sublimate when heated alone, or with tin or soda in the closed tube. Zinc, when heated with soda on charcoal, forms a de- posit, which> when warm, is yellow; when cold, white ; is tinged of a fine green by solution of cobalt, and is not fur- ther volatile in the oxidating flame. In solution, zinc is precipitated by potassa as a white gelatinous hydrate, easily redissolved in the excess of the alkali. CHEMICAL PROPERTIES OF MINERALS. 125 Tin forms a white deposit on the charcoal behind the assay, which takes a bluish-green color with the solution oi cobalt. The oxide is easily reduced by soda. -LeadTorms a sulphur-yellow deposit with a white border on the charcoal when heated in the oxidating flame, and with soda is easily reduced. The solutions of its salts are colorless, but give a black precipitate with sulphuretted hydrogen ; with sulphuric acid a white, and with chromate of potassa a yellow, precipitate. Cadmium produces, with soda, a reddish-brown or orange-yellow ring, with iridescent border on the charcoal, and also on platinum-foil. Manganese alone, melted with borax or salt of phos- phorus on the platinum wire in the oxidating flame, forms a fine amethystine glass, which becomes colorless in the reducing flame. In combination with other metals, the pulverized assay mixed with two or three times as much soda, and melted in the oxidating flame on platinum-foil, forms a bluish-green glass. Potassa or ammonia throws down from solutions of its salts a white hydrate, which, in the air, becomes gradually dark-brown. Cobalt, melted with borax in the oxidating flame, gives a beautiful blue glass. Minerals of metallic aspect must be first roasted on charcoal. The salts of protoxide of cobalt form bright-red solutions, from which potassa throws down a blue flaky hydrate, which becomes olive-green hi the air. Nickel, the assay, first roasted in the open tube and on charcoal, produces in the oxidating flame, with borax, a glass, which hot, is reddish or violet brown ; when cold, yellowish or dark red ; and by the addition of saltpetre, changes" to blue. In the reducing flame the glass appears gray. With salt of phosphorus the reaction is similar, but the glass is almost colorless when cold. The salts in solu- tion have a bright-green color, and with potassa, form a 126 A POPULAR TREATISE ON GEMS. green precipitate of liydrated nickel-oxide, which is un- changed in the air. Copper may in most cases be discovered by melting the assay (if apparently metallic, first roasted) wifh borax or salt of phosphorus in the oxidating flame, when an opaque recldish-brown glass is produced, a small addition of tin aiding in the result. In the reducing flame, the glass, when warm, is green ; when cold, blue. With soda, me- tallic copper is produced. A small proportion of copper may often be detected" by heating the assay, moistened with hydrochloric acid, in the oxidating flame, which is then tinged of a beautiful green color. Solutions of its salts are blue or green, and produce a brownisliTblack pre- cipitate, with sulphuretted hydrogen. Ammonia at first throws down a pale-green or blue precipitate, but in excess produces a very fine blue color. t Silver in the metallic state is at once known, and from many combinations can be readily extracted on charcoal with soda. From its solution in nitric acid, silver is thrown down by hydrochloric acid as a white chloride, which in the light soon becomes black, is" soluble in ammonia, and can again be precipitated from this solution by nitric acid as chloride of silver. Gold, when pure, is readily known, and is easily separated 'from its combinations with tellurium on charcoal. If the grain is white, it contains more silver than gold, and must then be heated in a porcelain capsule with nitric acid, which gives it a Wack color, and gradually removes the silver, if the gold is only a fourth part or less. If the proportion of gold is greater, the nitro-chloric acid must be used, which then removes the gold. From its solution in this acid the protochloride of tin throws down a purple precipitate (pur- ple of Cassius), and the sulphate of iron, metallic gold. Platinum, and the metals usually found with it, cannot CHEMICAL PROPERTIES OF MINERALS. 127 be separated from each other by heat. Only the Osmium- iridium strongly heated in the closed tube with saltpetre is decomposed, forming osmium acid, known from its pecu- liar pungent odor. The usual mixture of platinum grains is soluble in nitro-chloric acid, leaving osmium-iridium. From this solution' the platinum is thrown down by sal- ammonia as a double chloride of platinum and ammonium. From the solution evaporated, and again diluted, with cyanide of mercury, the palladium separates as cyanide of palladium. The rhodium may be separated by its property of combining with fused bisulphate of potassa, which is not the case with platinum or iridium. Cerium, when no iron-oxide is present, produces, with borax and salt of phosphorus, in the oxidating flame, a red or dark-yellow glass, which becomes very pale when cold, and colorless in the reducing flame. Lanthanium oxide forms a white colorless glass ; didymium, a dark amethyst- ine glass. Iron, the peroxide and hydrated peroxide, become black and magnetic before the blowpipe, and form, with borax or salt of phosphorus, in the oxidating flame, a dark-red glass, becoming bright-yellow when cold ; and in the reducing flame, especially on adding tin, an olive-green or mountain- green glass. The peroxide colors a bead of borax contain- ing copper oxide, bluish-green ; the protoxide produces red spots. Salts of protoxide of iron form a green solution, from which potassa or ammonia throws down the protoxide as a hydrate, which is first white, then dirty-green, and finally yellowish-brown. Carbonate of lime produces no precipitate. The salts of the peroxide, on the other hand, form yellow solutions from which the peroxide is thrown down by potassa or ammonia as a flaky-brown hydrate. Carbonate of lime also causes a precipitate. Chromium forms, with borax or salt of phosphorus, a 128 A POPULAR TREATISE ON GEMS. glass, fine emerald-green when cold, though when hot often yellowish or reddish. Its solutions are usually green, and the metal is thrown down by potassa as a bluish-green hy - drate, again dissolved in excess of the alkali. The chrome in many minerals is very certainly discovered by melting the assay with three times its bulk of saltpetre, which, dis- solved in water, gives with acetate of lead a yellow precipitate. Vanadium, melted on platinum wire with borax or salt of phosphorus, gives a fine green glass in the reducing flame, which becomes yellow or brown in the oxidating flame, distinguishing it from chrome. Uranium, with salt of phosphorus, forms in the oxidating flame a clear yellow ; in the reducing flame a fine green glass. With borax its reaction is similar to that of iron. Molybdenum forms in the reducing flame, with salt of phosphorus, a green ; with borax, a brown, glass. . Tungsten or Wolfram forms, with salt of phosphorus, in the oxidating flume, a colorless or yellow, in the reducing flame, a very beautiful blue glass, which appears green when warm. AYhen accompanied by iron, the glass is blood- red, not blue. Or melt the assay with five times as much soda in a platinum spoon, dissolve it in water, filter, and decompose the result with hydrochloric acid, which throws down the tungstic acid, which is white when cold, but citron-yellow when heated. Tantalium, as tantalic acid, is readily dissolved by salt of phosphorus, and in large quantity into a colorless glass, which does not become opaque in cooling, and does not acquire a blue color from solution of cobalt. Or fuse the assay with two times as much saltpetre, and three times as much soda, in a platinum spoon ; dissolve this, filter, and decompose the fluid by hydrochloric acid : the tantalic acid separates as a white powder, which does not become yellow when heated. CLASSIFICATION OF MINERALS. 129 Titanium in anatase, rutile, brookite, and titanite, is shown by the assay forming, with salt of phosphorus, in the oxidating flame, a glass which is and remains colorless ; in the reducing flame, a glass which appears yellow when hot, and whilst cooling passes through red into a beautiful vi^fet. When iron is present, however, the glass is blood- red, but is changed to violet by adding tin. When titanate of iron is dissolved in hydrochloric acid, and the solution boiled with a little tin, it acquires a violet color from the oxide of titanium. Heated with concentrated sulphuric acid, the titanate of iron produces a blue color. CHAPTER IV. CLASSIFICATION OF MINERALS. A MINERAL species was formerly defined as a natural in- organic body, possessing a definite chemical composition and peculiar external form. The account given of these properties shows that the form of a mineral species compre- hends not only the primary or fundamental figure, but all those that may be derived from it by the laws of crys- tallography. Irregularities of form arising from accidental causes, or that absence "of form which results from the limited space in which the mineral has been produced, do not destroy the identity of the speeies. Even amorphous masses, when the chemical composition remains unaltered, are properly classed under the same species, as the perfect crystal. The definite chemical composition of mineral species must be taken with equal latitude. Pure substances, such as they are described in works on chemistry, are very rare 130 A POPULAR TREATISE ON GEMS. in the mineral kingdom. In the most transparent quartz crystals, traces of alumina and iron oxide can be detected ; the purest spinel contains a small amount of silica, and the most ^brilliant diamond, consumed by the solar rays, leaves some ash behind. Such non-essential mixtures must be neglected, or each individual crystal would form a distiiHt mineral species. The isomorphous elements introduce a wider range of varieties, and render the limitation of species more difficult. ' Carbonate of lime, for instance, becomes mixed with carbonate of magnesia or of iron in almost innumerable proportions; and the latter substances also with the former. Where these mixtures are small in amount, variable in different specimens, and do not greatly affect the form or physical characters of the predominant element, they may safely be neglected, and the mineral. reckoned to that species with which it most closely agrees. "Where, however, the mixture is greater, and the two substances are frequently found in definite chemical proportions, these compounds must be considered as distinct species, espe- cially should they also show differences in form and other external characters. Amorphous minerals with definite composition must also be considered as true species. But when they show no definite composition, as in many substances classed as clays and ochres, they cannot be accounted true mineral species, and properly ought not to be included in a treatise on mineralogy. Some of them, however, from their import- ance in the arts, others from other circumstances, have re- ceived distinct names and a kind of prescriptive right to a place in mineralogical works, from which they can now scarcely be banished. Many of them are properly rocks, or indefinite combinations of two or more minerals $ others are the mere products of the decomposition of such bodies. Their number is of course indefinite, and their introduction CLASSIFICATION OF MINERALS. 131 tends much to render mineralogy more complex and diffi- cult, and to destroy its scientific character. In collecting the species into higher groups, and arrang- ing them in a system, several methods have been pursued. Some, like Mobs, have looke.d only at the external charac- ters, and asserted that they alone were sufficient for all the purposes of arranging and classifying minerals. Others, led by Berzelius, foave, on the contrary, taken chemistry as the foundation of mineralogy, and classed the species by their composition, without reference to form or physical characters. Neither system can be exclusively adopted, and a nat- ural classification of minerals should take into account all their characters, and that in proportion to their relative importance. Among these the chemical, composition un- doubtedly holds a high rank, as being that on which the other properties will probably be ultimately found to de- pend. Next in order is their crystalline form, especially as exhibited in cleavage ; and then their other characters of gravity, hardness, and tenacity. But the properties of minerals are as yet far from showing that subordination and co-relation which has been observed in the organic world, where the external forms and structures have a direct reference to the functions of the living being. Hence, even when all the characters are taken into account, there is not that facility in classifying the mineral that is presented by the other kingdoms of nature. Many, or rather most, of the species stand so isolated that it is scarcely possible tp find any general' principle on which to collect them into large groups, especially such groups as, like the natural families of plants and animals, present important features of general resemblance, and admit of being described by common characteristics. Certain groups of species are indeed united by such evident characters, that they are 132 A POPULAR TREATISE ON GEMS. * found together in almost every method ; but other species are not thus united, and the general order of arrangement is very uncertain. Hence, though some classifications of very considerable merit have been proposed, no natural system of minerals commanding general assent has yet appeared. . The arrangement followed in this treatise is chiefly founded on that proposed by Professor Weuss of Berlin. We have, however, made considerable changes, which the progress of the science and the more accurate knowledge of many species require. This classification appears to us to come nearer than, any other we have seen to a natural system, which in arranging and combining objects takes account of all their characters, and assigns them their place, from a due consideration of their whole nature, and is thus distinguished from artificial systems, which classify objects with reference only to one character. Besides species, two higher grades in classification seem sufficient at once to exhibit the natural relations, and to facilitate .an easy and complete review of the species com- posing the mineral kingdom. These are families and orders. In forming the families, those minerals are first selected which occupy the more important place in the composition of rocks, and consequently in the crust of the globe. Thus quartz, felspar, mica, hornblende, garnet, among siliceous minerals; calc-spar, gypsum, rock-salt, less so fluor spar and heavy spar, among % those of saline composition, stand out prominently as the natural centres or representatives of so many distinct families. To these certain metallic miner- als, as iron pyrites, lead-glance or galena, blende, magnetic iron ore, the sparry iron ore, and a few more, are readily associated as important families. But the minerals thus geologically distinguished are not sufficient to divide the whole mineral kingdom into convenient sections, and addi- CLASSIFICATION OP MINERALS. 133 tional groups must be selected from the peculiarity of their natural-historical or chemical properties. Thus the zeo- lites are easily seen to form such a natural group. The precious stones or gems also, notwithstanding their diverse chemical composition, must ever appear a highly natural family, when regarded as individual objects. Their great hardness, tenacity, high specific gravity without the me- .tallic aspect, their brilliant lustre, transparent purity, and vivid colors, all mark them out as a peculiar group. Only the diamond, which might naturally seem to take the chief place in this class, differs so much, not only in elementary composition, but in physical properties, that it must be assigned to a different place. Round these .species thus selected, the other Jess import- ant minerals are arranged in groups or families. It is evi- dent? that no precise definition of these families can be given, as the connection is one of resemblance in many points, not of identity in any single character. In other words, it is a classification rather according to types than from definitions, as every true natural classification must be. The same cause, however, leaves the extent of the families somewhat undefined, and also permits considerable license in the arrangement of species. But both circum- stances are rather of advantage in the present state of the science, as allowing more freedom in the grouping of spe- cies than, could be obtained in a more rigid system of clas- sification. In collecting the families into orders, the guidance ot chemistry is followed rather than of natural history, thougli the latter is also takenjnto consideration. Chemical names are assigned to the orders, but still regarded as names de- rived from the prevailing chemical characters, and not as definitions. Hence it must not be consider^! an error should two or three mineral species be found in an order 134 A POPULAR TREATISE ON GEMS. with whose name, viewed as a definition, they may not agree. Guided by these and similar considerations, minerals may be divided into the following orders and families : ORDER I. THE OXIDIZED STONES. Families. -1. Quartz. 8. Serpentine. 2. Felspar. 9. Hornblende. 3. Scapolite. 10. Clays. 4. Haloid stones. 11. 'Garnet. 5. Leucite. 12. Cyanite. 6. Zeolite. 13. Gems. 7. Mica. 14. Metallic stones.' ORDER II. SALINE STONES. families. 1. Calc spar. 4. Gypsum. 2. Fluor spar. 5. Kock salt. * 3. Heavy spar. ORDER III. SALINE ORES. Families. -1. Sparry iron ores. 8. Copper salts. 2. Iron salts. 4. Lead salts. ORDER IV. OXIDIZED ORES. Families. I. Iron ores. 4. Red copper ores. 2. Tinstone. 5: White antimony ores. 3. Manganese ores. ORDER V. NATIVE METALS. Form only one family. ORDER VI. SULPHURETTED METALS. Families. I. Iron pyrites. 4. Gray copper ore. 2. Galena. 5. Blende. 3. Gray antimony ore. 6. Ruby-blende. ORDER VII. THE INFLAMMABLES. Families. I. Sulphur. 4. Mineral resins. Diamond. 5. Combustible salts. Coal. PART II. THE GEMS. + * PRECIOUS STONES OK GEMS. PRECIOUS stones or gems are such minerals as, either from their beauty or other valuable properties, have become the subject of the arts or trade, and are used as ornaments, or employed by jewellers. In order to appreciate more fully such minerals as may possess superior virtue, it is our pres- ent object to consider them in reference to their scientific and practical value. DIVISION OF GEMS. Gems are generally classed as follows: 1st, real gems, or jewels ; and 2d, semi-gems, or also precious stones. The first comprise such minerals as combine, within a small space, either vivid or soft and agreeable colors, with a high de- gree of lustre, usually termed fire, as well as hardnes's; the second possess these characters in^a less degree, and occur often semi-transparent or translucent, and in larger formless masses. It is, however, impossible to draw a Gtrict line between them, as the conventional value put upon the one or the other also affects their character ; for very often some, which are generally considered as belonging to the second class, may be valued, for their peculiar prop- erties, much higher than some of the first class. 136 A POPULAR TREATISE ON GEMS. Those species of minerals which are generally considered real gems are Diamond, Garnet, Sapphire, Tourmaline, Chiysoberyl, Rubellite, Spinelle, Essonite, Emerald, Cor.dierite, Beryl, . lolite, Topaz, Quartz, Zircon, Chrysolite. The rest are considered as semi-precious stones. COLOR, GRAVITY, AND HARDNESS OF GEMS. The precious stones possess the colors in their highest perfection, and their principal and intrinsic value depends mostly upon this property ; and as most gems occur in va- rious colors, the following table will exhibit them, along with their specific gravity and hardness : LIMPID "GEMS. SPECIFIC GRAVITY. HAKDNESS. Zircon 4-41 to 470 7'5 Sapphire 3-9 4-20 7- Diamond 3-5 3'6 10' Topaz (Pebble) 3-49 3-56 8- Eock Crystal (False Diamonds, Lake George, Trenton Falls) 2'69 7* Beryl, Aquamarine , 2-67 2'68 7'5 BED GEMS. Zircon, Hyacinth 4-41 4-70 7'5 Garnet (Oriental Garnet) 4'0 4-2 6'5 Sapphire, Ruby .. 4>0 4'2 9' Garnet, Bohemian Garnet. Pyrop 3'7 3'8 6'5 Spinelle, Ruby Spinelle, Ruby Balais 3'49 3*7 8- Diamond 3-5 3*6 10- Essonite 3'5 3-6 7' Topaz. "Brazilian Topaz (often burnt) 3'52 8'56 8- GRAVITY AXD HARDNESS OF GEMS. 137 SPECIFIC GRAVITY. HABDUKSS. Tourmaline, Siberite, Eubellite 3*0 to 3-30 6*5 Rose Quartz. Bohemian Ruby 2'50 2*63 7' Carnelian 2'5 2'6 ? YELLOW GEMS. Zircon 4-41 4'50 7 '5 . Sapphire. Oriental Topaz ; '. . 4-0 8- Chrysoberyl 3'65 3'80 8'5 Topaz. Brazilian, Saxonian, and Syrian Topaz 3'50 3'56 8' Diamond '. . . . 3-5 3-6 10* Beryl ; 2'67 2'7l 1'S Rock Crystal, Citron 2'60 2'69 7- Fire-opal 1-90 2-12 5-5 GREEN GEMS. Zircon 4-41 4'50 Sapphire, Oriental Chrysolite, and Emerald .. 3'9 4'00 V Malachite 3>6T 3-5 Chrysoberyl 3'59 3'75 8'5 Spinelle , 3-58 3'64 8' Diamond 3-5 3'6 10' Topaz. Aquamarine 3-49 3-56 s* Chrysolite 3'33 3'44 6'5 Idocrase 3'08 3'40 6'5 Tourmaline (Brazilian and Maine) 3'00 3-30 6-5 Emerald.. * 2'67 2'73 7'5 Berj'l 2-67 271 7'5 Prase... 2-66 2'6S f- HeHotrope 2'61 2-63 7" Chrysoprase 2'5S 2-60 7- Felspar, Amazon Stone 2'50 2'60 6' BLUE OEMS. Sapphire 3'90 4'00 8' Disthene (Kyanite) '. , . 3'50 S'67 5' Spinelle 3'58 3'64 8' Diamond 3'5 3'6 10- Topaz. Brazilian Topaz 3-49 3'5ft S- Tourmaline, Indigolite : 3'00 3'30 6'5* Turquoise 2*86 3*00 6- Beryl, Aquamarine .* 2-67 2*71 7'5 Dichroite (loUte) 2-58 2-60 7* 138 A POPULAR TREATISE ON GEMS. SPECIFIC GRAVITY. HARDNESS, Hauyne 2-47 5' Lazulite 2-30 5- * VIOLET GEMS. Garnet 4'0 to 4-2 6'5 . Sapphire, Oriental Amethyst 3 ! 9 4'0 9- Spinelle '. 3'58 3'64 8* Axinite 3'27 6'5 Tourmaline 3'00 3'30 6'5 Amethyst : 2-65 2'7S 7' BROWN GEMS. Zircon 4'41 4'50 7'5 Garnet ' 4-00 4'20 6'5 Essonite 3-53 3'60 7' Diamond 3'50 3-60 10' Toifrmaline 3'00 3-30 6*5 Smoky Quartz .2-69 2*70 7' BLACK GEMS. Diamond 3-50 3'60 10* Tourmaline 3'00 3'30 6' Eock Crystal, Morion 2'69 2'7l 7' Obsidian 2-34 2'39 6"-o Pitch Coal . 1-29 1-35 2- CannelCoal : 1*23 1'27 2' GEMS DISTINGUISHED FOK THEIR VARIOUS SHADINGS OF COLOR AND LIGHT. Garnet 4-00 4'20 6-5 Sapphire, Star Sapphire 3'90 4'00 9 - Chrysoberyl 3*70 3'SO 8'5 ' Hypersthene 3'38 6- ' Labrador Spar 2-71 2'75 6- Dichroite 2'58 2'60 7' Cat's-eye .* 2'56 2'73 7' Adularia 2-50 2'60 6' Felspar 2'50 2'60 6- Precious Opal 2-00 2-10 5'5 Hydrophane 1'90 2'00 5- A number of precious stones do not possess a local color, COMPOSITION OF GEMS. 139 but merely a tinge or a shade of color ; and these we dis- tinguish by the following degrees of dark, high, light, and pale colored, or tinged. Another distinction may be de- tected in precious stones as possessing either one or more colors, or a variegated color ; or as being spotted, painted, stained with the different colors. These latter characters are, however, more proper to the semi or common precious stones, than to gems. CHEMICAL CHARACTERS. Although mineralogy could nqt exist, as a science, with- out the aid of chemistry, and whole systems or classifica- tions have been established, as well as the constituent parts of minerals determined, by the knowledge of Chemical char- acters, still it is difficult to resort to chemical means for dis- tinguishing the gems or precious stones, as they would be destroyed by such an examination, and we can, for that purpose, only employ splinters or fragments. The most simple mode of proceeding is to test 1st, Their greater or less fusibility, with or without a flux ; 2d, Their behavior before the blowpipe, an instrument highly convenient, and, indeed, indispensable to the miner- alogist ; and, 3d, The action of the acids upon them. All of these means, however, have not an effect upon all gems, as many of them, for instance, are either infusible, or fusible with the greatest difficulty by the addition of a flux. COMPOSITION OF GEMS. The attention "of writers, as far back as 1502, had been directed to the establishment of some hypothesis as to the composition .and origin of the gems, and many fabulous* views were entertained in respect to their formation. There was also connected with some hypotheses a species 140 A POPULAR TREATISE ON GEMS. of medical superstition as to their effect. Boyle (1672) thought that all gems were originally formed from clear limpid water, and that they received their color and other properties from their metallic spirit. Others considered a peculiar earth, called the noble or precious earth, as the principal ingredient of the precious stones. Bruckman (1778) recognized quartz as the principal of the gems. Bergman thought that gems were all composed of the same ingredients, such as alumina, silex, and lime, and that the different proportions produced the different species ; and the older mineralogists determined the character of the gems by their hardness, lustre, structure, and resistance to acids. But modern chemistry has ascertained the compo- nent parts, and other characters of gems, with more cer- tainty, and it is satisfactorily proved that the principles they contain are the earths, such as silica, alumina, and lime ; that some contain a peculiar earth (such is the case with the zircon, emerald, and chrysoberyl), and that the diamond, at the head of gems, consists of pure carbon, / 4 Oxide of Cobalt 5 .. 15 / Oxide of Copper .. .. 8 Oxide of Chrome . . . . .'. Ys Colored glass is also very frequently cut in forms and shapes so as to resemble gems, and the various colors are produced by melting the best qualities of glass materials with the folio whig oxides : Yellow is produced by charcoal, antimonite of potassa, ' silver, and oxide of uranium. Blue, by oxide of cobalt, and a mixture of copper and iron. Green, by oxide of copper or of chrome, or by antimo- nite of potassa, litharge, and cobalt. Red, by gold, suboxide of copper, and oxide of iron. Violet, by manganese. Black, by protoxide of uranium, iridium, platinum, and by a mixture of manganese, copper, iron, and cobalt. White, by oxide of tin, arsenic, and bone'-ashes. By combining one or more of these oxides various shades and hues may be obtained ; the yellow glass of antimony may be shaded more into orange by the use of a little oxide of iron ; the purple-red of gold passes into carmine by employing silver with gold ; the blue of cobalt may be shaded into purple by a little gold ; into green by antimony, 176 A POPULAR TREATISE ON GEMS. or other yellow colors ; a rich grass-green is obtained from oxide of chrome, with a little antimony and litharge ; a brilliant emerald-green from a mixture of oxide of uranium and nickel ; oxide of nickel alone yields a hyacinth-red. The Bohemian garnet is prepared by fusing together 100 parts quartz, 150 parts red lead, 30 parts potash, 20 parts fused borax, 5 parts crude antimony, 5 parts manganese, and 6 parts fulminating gold ground up with oil of turpen- tine. Turquoise is imitated by oxides of copper and cobalt. Opal, by adding oxide of tin and bone-ashes to the glass, in small quantities. The following colored pastes were recommended by me twenty years ago, to the American manufacturers of colored glass, and have all proved successful : JStrass. This is the basis for ah 1 pastes ; it is very hard, and gives sparks when rubbed on steel. 1 ounce of powdered glass, 2 drachms burnt borax, 3 drachms " quartz, 40 grains of saltpetre, 3 ' " red lead, 30 " white arsenic. This composition is exposed to a white heat in a covered crucible for thirty hours. Ruby. I ounce of powdered rock-crystal 3 drachms of red lead, or quartz, 15 grains of eassius purple, i ounce of dried carbonate soda, 8 " metallic antimony, 4 drachms of burnt borax, 8 " oxide manganese. It " saltpetre, Or by taking 1 ounce of powdered rock-crystal, 40 grains saltpetre, i " dry carbonate soda, 15 " purple cassius, 80 grains of burnt borax, 1 drachm of sal ammonia. IMITATIONS OF GEMS. Take It ounce of ground rock-crystal, 6 drachms of dry soda, 2 " " borax, Or mix 1 ounce of rock-crystal, y " dry soda, 3 drachms " borax, It " red lead, Sapphire. 2 drachms of red lead, 1 " saltpetre, 1 grain, of carbonate cobalt. .t drachm of saltpetre, i grain of carbonate cobalt, 15 " " copper. By means of the carbonate of copper. It ounce of rock-crystal, 6 drachms of soda, 1 borax, Take- it ounce of rock-crystal, 6 drachma of dry soda, 2 " " borax, 2 " red lead, 1 ounce of rock-crystal, t " dry soda, 2 drachms of dry borax, 2 " . red lead, 9 drachms of rock-crystal, 8 " dry soda, 2 " red lead, 1 " saltpetre, It ounce of rock-crystal, t " dry soda, 8 drachms of burnt borax, 2 " red lead, 20 grains of saltpetre, 1 drachm red lead, t " saltpetre, t " carbonate of copper. Emerald. 1 drachm of saltpetre, 20 grains of red oxide of iron, 10 " green carbonate of copper. Green Color. 40 grains of saltpetre, It " carbonate cobalt, 10 " " chrome. Canary. 80 grains of oxide of uranium, 3 " carbonate of copper, oxide of tin, white b'nt bone-ashes. Chrysoprase. 2 drachms of white bone-ashes, 2 grains of carbonate of copper, 4 " red oxide of iron, 6 " oxide of chrome. 178 A POPULAR TREATISE ON GEMS. Opal. 9 drachms of rock-crystal, 15 grains of saltpetre, 8 " dry soda, /io " cassias purple, 2 " burnt borax, Iff " bone-ashes, li " red lead, 2 " muriate silver. Aquamarine. Is ounce of rock-crystal, 1 drachm of saltpetre, 1 " dry soda, * 6 grains of red oxide of iron, 8 drachms of burnt borax, 2 " carbonate of copper. 2 " red lead, Hyacinth. The above mixture, with the addition of ten grains of the oxide of manganese. Garnet. 9 drachms of rock-crystal, 40 grains of saltpetre, 8 " dry soda, 5 " oxide of manganese, 2 " burnt borax, 3 " " iron, li " red lead, 1 " cassius purple. Rubellite, Red Tourmaline. 1 ounce of rock-crystal, 1 drachm of red lead, 1 " dry soda, H " ' saltpetre, 8 drachms of burnt borax, 8 grains of oxide of nickel. Indigolite^ or Blue Tourmaline. The above mixture, with the addition of the carbonate of cobalt. Chrysolite. 6 drachms of rock-crystal, 1 drachm red lead, 2 " dry soda, 10 grains of saltpetre, 14 " burnt borax, 2 " oxide of manganese. Amethyst. ' But 1 grain of the oxide of manganese to each ounce of the mass. IMITATIONS OF GEMS. 179 Turquoise. In the above mixture use instead of the manganese 5 grains of dry verdigris, 20 grains of bone-ashes. 3 " powder blue, Lazulite. By adding to former mixtures^ 2 grains oxide cobalt, 1 drachm of burnt bone-ashef. Agate. By mixing together several frits and adding oxide of iron, several varieties of agate are obtained. It will now be necessary to show the distinguishing char- acters between the real and artificial gems, as they so closely resemble each other that a superficial inspection will not always enable the examiner to discriminate be- tween them ; they are as follows : 1. The hardness ; which may be tested on the grinding machine ; with fine quartz sand it will immediately attack the pastes, or by scratching with a real onyx, to which the pastes will immediately yield. 2. The small air-bubbles in the pastes, may more of less be detected with a good magnifying glass. 3. The cold touch will never remain for any length of time on the pastes as it will on the real gem. 4. The breath remains much longer on the pastes, on account of their bad conducting power, than on real gems. The specific gravity and electricity, may likewise indicate the difference, but I never depended on them alone, and I will mention that I once examined the specific gravity of an artificial topaz which fully corresponded with that of a Brazilian topaz. Electricity will indicate the difference between real and artificial gems by the length of its con- 180 A POPULAR TREATISE ON GEMS. tinuance; for real gems retain, after being rubbed, their electricity for from six to thirty-two hours, whereas, the artificial ones only retain it from forty to sixty minutes. _Z?. The Doublets. This mode of imitating real gems is called doubling, when a quartz, cut and polished, is ce- mented by means of gum mastic to another colored paste, whereby the whole stone assumes the color of the lower paste. When a real gem' is employed instead of quartz (as the surface and the quartz or paste is cemented below), it is called half doubling. This adulteration is carried on to a very great extent in the East Indies, where they paste any thin gem to a paste corresponding in color. The concave doubling is effected by excavating the inside of a quartz or paste. The cavity being filled with a colored fluid, and the other part afterwards cemented on it, will, when well executed, present so uniform a color that it is difficult even for a judge to detect the deception. The surest method of detection is to put the specimen in ques- tion in hot water or alcohol, by which the gum mastic will be dissolved. When set, the only way of finding out the adulteration, is to put it reversely on the nail of the thumb, when the false refraction of light or the rainbow colors will, with certainty, determine its identity. C. The Burning. This mode of adulterating the real gems, is performed by coloring cut and polished quartz specimens. and throwing them into a solution of permanent pigments, such as a solution of indigo, decoction of cochi- neal, solution of ammoniacal copper ; the small cavities produced by the heat will absorb the fluids. The topaz is burnt by itself, with or without the absorption of a pig- ment, as also the spinelle, and the quartz ; chalcedony is, however, frequently burnt to imitate the onyx, and to en- grave thereon cameos and intaglios. It 'may be remarked, however, that since the introduc- GEMS FOB OPTICAL PURPOSES. 181 tion of colored pastes, very few adulterations of this kind are now practised, and we see but rarely such doublets and burnt stones. PRICE OF AJSD TRADE IN GEMS. It is difficult to determine the price of gems without reflecting upon all the circumstances relating to them, such as beauty and uniformity, the play, the lustre, and the vivacity of the colors, and also on the perfection of the cut, the polish, the rare locality, the size of the individual gems. It depends upon the trade of the various countries whence they come, and what quantity of such valuable gems may be had at one time at any of the great cities : we find that diamonds re often sold at a much less price in London and Paris than in Brazil. The principal trade, however, is as yet carried on in Brazil and the East Indies, although it is in no comparison so prosperous as in former years. The gems are sold by weight, as carat and grain-. One carat is equal to four grains, and forty-four carats are equal to one ounce. The name carat is derived from the word kuara, the coral-tree (erythrina), the red pods of which", when dry, were formerly used for weighing gold dust, and each of them weighs four grains, which is equal to one carat. GEMS FOR OPTICAL PURPOSES. A few- years ago, Massrs. Trecourt and Oberhauser laid before the Parisian Academy lenses of the diamond,, sapphire, and ruby, which were used in connection with glass lenses in microscopes ; they were of nine-tenths milli- metre, in diameter. The diamond lens magnified two hundred and ten times, that of sapphire, two hundred and fifty-five times, and that of ruby, two hundred and thirty- five times, in linear extension. 182 A POPULAR TREATISE ON GEMS. A letter was lately published from Sir David Brewster, on a curious optical phenomenon that had occurred in the construction of a diagonal lens. The diamond, previous to working, had all the appearance of internal brilliancy ; but, after being polished, it presented a series of stratified shades, which rendered it useless for the required purpose. It afterwards appeared that lapidaries were acquainted with this appearance, which rendered them extremely un- willing to take the risk on themselves, of cutting up dia- monds for optical purposes. On a minute examination of this phenomenon, it appeared that these different shades occurred in regular strata, each section being about the one-hundredth part of an inch, and each stratum having a different focus, and being of a different degree %f hardness and specific gravity. The inferences drawn from the above facts were : that the diamond was a vegetable substance, and that its parts must have been held in solution and sub- jected to different degrees of pressure at different stages of existence. If, on the contrary, as it has been generally believed, it is subject to the laws of crystallization, its crys- tals must necessarily be homogeneous. 1 Stt.Beiyl. 2 Emerald. 3 Rube^e. ^BrazaTopas. 5 Rulr/. 6 Star 7 Opal. 8 Hyacinth.. PART III. CONSIDERATION OF THE INDIVIDUAL" GEMS. DIAMOND. DIAMOND: Diamant (German), Adamant (of the an- cients), Almas (Oriental), Diamant (French). The name Diamond is derived from the Greek, Adamas, meaning in- vincible, and referring to the hardness of the gem. The Syrians are said to have first known the diamond, and it was in early ages the subject of trade to the people of the East. The Carthaginians are said to have carried on their trade with the Etrurians, who procured diamonds from the interior of Africa. Pliny mentions six species of diamonds, among which, however, the Indian are to be considered the true, in contradistinction to the quartz crystals, which were likewise called diamonds in those times. The dia- mond was highly esteemed, and many medicinal virtues were attributed to it, particularly against mania, and as an antidote for poisons ; it was worn in the rough state. The art of cutting it with its own powder was discovered in 1476, by Lewis Van Berghen. In the beginning it was cut in the table-form, with one row of facets on the surface ; afterwards, in 1520, the rhomb cut was adopted : the form of brilliants was invented in the reign of Louis XII. Cardinal Mazarin was the first who had diamonds polished in this form, some of which yet belong to the crown of France. For a long 184 A POPULAR TREATISE ON GEMS. time philosophers vainly speculated as to the nature of the diamond ; first it was considered as a mineral, consisting of silica ; but Newton was the earliest (1675) who expressed himself as to the constitution of diamonds. He judged, from the great refraction of light, that it must be a com- bustible body, and a series of experiments with it, tested afterwards by different naturalists, proved the same to be pure carjbon. The first trial was made in 1694, by the members of the Academy at Florence, by whom diamonds were volatilized within the focus of a mirror. Bergman first classified the diamond among combustible bodies, and mentions having cut off the head of the gems. Various views existed in regard to the origin of the dia- mond : some considered it as a secretion of a vegetable substance ; others as originating from volcanic or plutonic revolution. The Indians believe diamonds are continually regenerating and growing to this date ; and the inhabitants of Pharrah, in Hindostan, affirm that the quantity of dia- monds by no means decreases, but on the contrary, the soil will yield a new supply fifteen or twenty years from the time it is exhausted. Numerous experiments have been instituted to produce an artificial diamond from several substances which contain carbon, and by the application of a high degree of heat. The late Dr. Hare, in Philadelphia, succeeded in melting down mahogany charcoal so as to produce a metallic ap- pearance, by his deflagrator. Professor Silliman likewise made similar experiments with plumbago, which produced small globules, some of which were so transparent that they could not be distinguished from the genuine diamond. Professor Yanuxem, who examined the globules obtained from fused charcoal, found them to contain iron and carbon, which led him to the conclusion that the charcoal had not undergone a real fusion. Cagniard de Latour pretended DIAMOND. 185 to have discovered the ingredients for imitating diamonds of some size ; but Thenard proved those small crystals of the appearance of diamonds to be some silicates of pecu- liar composition, which, according to Arago, polarized light in a different angle from that of diamonds. All speculative experiments to imitate this most precious gem by the various compounds of carbon, have hitherto proved abortive. The diamond is found crystallized mostly in the form of an octahedron (composed of t\vo four-sided pyramids, united by their bases), or rhombic dodecahedron, rarely of a cube ; but the planes of the angles, are often rounded or bevelled. The simple octahedron is pretty rare, and still more so the cube ; but the dodecahedron, either simple or complicated, is very frequent ; the crystals are sometimes hemitrope. In the museum of tne School of Mines are some fine macles, composed of two crystals crossing each other at right an- gles. The foliated passages are distinctly parallel to the faces of the octahedron, in which direction they may always be split. The fracture is conchoidal ; surface smooth, often rough or striped, and sometimes covered with a scaly crust; it is transparent, also semi-transparent; of an. ex- ceedingly vivid lustre, called the diamond or adamantine lustre, and when polished, of splendid fire ; it is limpid, and likewise passing into the greatest variety of shadings from white and gray, sometimes from yellow, green, and brown. The diamond being the hardest 'of all substances, yields to no file ; scratches all other minerals, and is not touched by any. This character has become the most important of the diamond since the late discovery of the amorphous or compact diamond. It is very frequently tinged light-green, but more rarely with orange, red, blue, or black ; but' in setting, these shades disappear, particularly in the smaller diamonds ; but there are also known diamonds of rose and 186 A POPULAR TREATISE ON GEMS. pistachio-nut green colors. The blue color is very rare. The blue diamond of Mr. Hope, of London, is one of ex- treme beauty and rarity, and is of immense value; the yellow diamond in the Museum of Natural History, in Paris, is likewise very remarkable for its color and size. The black diamond, which is perfectly black, although plainly crystallized, occurs most frequently in small bristled balls, but crystalline points ; the crystals are very small, grouped together in an irregular manner, and extremely refractory to the cut ; it is considered the hardest of all diamonds. The green diamond is also very rare, but I have seen some beautiful specimens in the Jardin des Plantes and in Freiberg, the first in the cabinet of Abbe Hatty, and the latter in the cabinet of Werner. Its streak powder is- white or grayish ; it becomes phosphorescent by the rays of the sun, and electric by rubbing, which property it retains for half an hour; its specific gravity is 3'5-3'6 ; it does not alter before the blowpipe ; it burns, however, at a high degree of heat, and in atmospheric air with a bluish flame ; its touch is very cold ; it consists of carbon. The diamond bears the same name in trade, but is changed according to its cut; the blackish and brownish diamonds are called the Savoy diamonds (Diamants Savoyards). The compact and amorphic diamond was first brought to notice by the experiments of Mr. Dufrenoy, about five years ago, as being the transition from the crystallized to the compact condition, on account of its hardness and specific gravity, and has become a great article of commerce ; it cuts glass, scratches quartz and topaz, has a specific gravity of S^V 3'52, and is completely consumed in oxygen gas; it occurs in kidney-shaped and irregular angular masses, but not in pebbles ; the exterior is generally black, sometimes resem- bling the graphite; somewhat resinous lustre, and fre- quently its form is very singular, the outside coating being DIAMOND. 187 black and resinous, the interior forming a crystalline ker. nel, vitreous and lamellar, like the diamond ; it is reduced to powder, and used for polishing and assisting in the cut- ting of the diamond. The largest specimen of the compact diamond weighs about 46 carats, and belongs to Mr. Hem- erdinger ; and a compact diamond in the Museum of Natu-" ral History at Paris, weighing about seventeen carats, is valued at fifteen hundred francs. The original bed of the diamond is not yet known, and on this point opinions are much divided. In the East Indies we find it in a conglom- erate of sandstone, consisting of quartz grains, and disinte- grated by the ferruginous sand ; and in the mountain chain Ralla-Malla, in Hindostan, between 95 and 98 E. L. Some of the celebrated diamond mines consist of a breccia from argillaceous slate, quartz, lime, and sandstone; the boulders and the sand of deserts and rivers yield diamonds mostly rounded or in a granular form. The richest dia- mond mines are those of Roalcorda, at the junction of the rivers Bimah and Ristna; Golconda, along the shore of the Pennar, Sumbhulpra, and Bundelkened, in the neigh- borhood of Pannah, where one thousand laborers are kept employed. Visapur, Hydrabad, &c., on the island of Bor- neo, likewise yield diamonds ; and, according to Jameson, diamonds were found in the Indies in the coal formation. In Brazil, they were discovered, in 1728, by chance, hav- ing been always thrown aside with the flint and other refuse of the washings of gold, until an inhabitant, who had some knowledge of rough diamonds, collected a large num- ber, and carried them to Portugal, and acquired by their sale a great fortune. Another, who was informed of the operations of the first, shared an equally good fortune. The government's attention was drawn to the matter, and it was declared, in 1730, that all diamonds found there belonged to the crown. 188 A POPULAK TREATISE OX GEMS. Diamonds are found in the talcose chlorite schist, and in a breccia, consisting of ferruginous clay, quartz pebbles, sand, and oxide of iron fragments ; and also in a secondary bed, accompanied by gold, platina, topaz, beryl, chryso-' beryl, tourmaline, kyanite, amatose, spinelle, corundum, and garnet. They are found particularly in the valley oi Sejues, along the rivers Jequetinhonha and Pardo, which run into .the diamond district. These carry most diamonds by. The dykes and brooks of the district contain more or less rich diamonds, which are found there in recent and older beds. Beyond the diamond district, the diamond is likewise found in the province of Minas Geraes on the Serro de St. Antonio, in the Serro Frio, and in the rivers Aboite, Andaja, da Saneno, da Prata, and several other places, such as the right bank of the Rio San Francisco, and Matto Grosso, and in the beds of Rio Pardo and Rio Vel- has ; in the mines of Riven and Cuithe, and all along the valley of Peruguado river, in the. province of Bahia, in some of the tributaries of the Rio Doce, on the banks of the Cachoine. The rocks in which recently diamonds have been found consist of the itacolumite, a micaceous sandstone, accompanied by mrca-schist, accidentally trav- ersed by quartz veins. This is the prevailing rock in the Serro de St. Antonio, in which the Jequetinhonha rises in the Serro da Matta da Corda, on the eastern slope of which the tributaries of the Rio Francisco rise ; and in the diamond district of Tibagy, very rarely in the alluvials of ancient rocks. The gold, diamonds, and other fine stones, are always imbedded in the lower part of the alluvium. Experience -has shown the richest localities to be in Curran- linho, Datas, Mendanho, Cavallo-Morte, and Caxoeira de Inferno, Avhere the alluvial soil is from eight to twenty feet thick, and is composed almost entirely of silicious sand, strongly colored by argillaceous iron, which forms a DIAMOND. 189 species of cement of pebbles of quartz, milky quartz, and itacolumite, which form a coarse pudding-stone, called casoelho, and which is considered by the diamond- washers a sure sign of the diamond. Dr. Cliffe, the proprietor of a diamond mine in Brazil, has given much information on this subject. In Russia, the first diamond was discovered in July, 18^9, by Humboldt and Rose, when on their journey to Siberia, on the west side of the Uralian mountains, in the gold-washing establishments of Krestowosdwisheaski, be- longing to Count Schuwalow. The locality, in connection with the other circumstances of the place where the dia- mond was found, bears a striking resemblance to the dia- mond district of Brazil. The predominating rock of the spot on the Uralian mountains is a quartzose chlorite, tal- cose schist (itacolumite), with an admixture of iron pyrites and mica, wherein we find beds of red oxide of iron, talcose schist, limestone, and dolomite. In the valley of Poludenka and Aedephskoi the diamonds are found among the "debris of the mountains, accompanied by quartz, itacolumite, brown hematite, talcose slate, dolomite, chalcedony, ana- tase, gold, and platina ; it is not yet decided to what for- mation this rock originally belongs. The production of diamonds is twofold; either they are dug out from the earth, or they are collected in the sand of rivers. If in the latter way, they are more or less rounded, wedged, and rubbed off; whereas the former appear coated with an earthy, pale gray, yellow, or rose-red, rarely with a blue or green crust. Many valuable mines have been relinquished in the East Indies since the discovery of diamonds in Bra- zil. The locality of the finest diamonds is at present in the neighborhood of Sumbhulpore. Two tribes, called the Thata and Tora, living in sixteen villages, occupy them- selves particularly with searching for diamonds, beginning 190 A POPDXAE TEEATISE ON GEMS. in the month of November, and continuing until the L mencement of the rainy season, more especially in the bed of the Mahanudi on its left shore, where some other small rivers, Maund, Reloo, Eeb, &c., empty into it. Four or five hundred individuals, consisting of men, women, and children, are examining continually all the spots of the river from Cauderpoor to Longpoor, a distance of about one hundred and twenty miles, till the stream is imped'ed by the rocks ; and likewise all excavations or other cavities of the beds where any alluvial deposits may be traced. All their implements consist of a pickaxe (ankova), a board five feet in length, excavated three inches in the middle, but provided with its border (daer), and a smaller similar implement, called by them kootla, both of the shape of a shovel. The process is very simple : they first dig the earth with the axe, and let it accumulate in heaps. along the shore; the women afterwards take it on their large shovels, and allow the water to run over the earth ; they then pick the flints and coarse gravel out of it, and re- moving the residue on smaller shovels, spread it out, and examine it very carefully, separating from it the diamonds and grains of gold. Another method pursued in the East Indies is to surround a small plain where the diamonds are expected to be found, with a w r all two feet high, under which water is permitted to run by -several openings ; after having thrown a good deal of earth within the wall, and having allowed the water to pass through two or three times, the larger stones are picked out, the residue dried, and the diamonds selected as before. The washing establishments of the diamond in Brazil, particularly in the celebrated district Tejuco, on the Rio San Francisco and its adjoining smaller rivers, are con- ducted in the following manner : In order to get at the bottom, or soil of the river, means DIAMOND. 191 are used for leading the water at a certain spot in a differ- ent direction, and then that part of the bed of the river is allowed to dry out, and the sediment consisting of a conglomerate of .quartz pebbles, kept together by oxide of iron, is brought to one place for washing. ' It is a large bench of triangular form, so as to keep from twenty to thirty negroes busy: in the middle of this bench is a gutter, with which is connected a trough, inclined some- what, in order that the water may run down voluntarily, but so that it may be stopped by putting loam at the end ; and another gutter with a trough is joined further down. The negro who has collected in the dry season a large quantity, of the sediment, is occupied in the rainy season in putting from fifteen to eighteen pounds at a time into the trough, spreading it there, and allowing so much water to run over it, until it runs off quite clear from the lower trough, but at the same time keeping the trough continu- ally moving. He then begins to pick out the larger stones from the earthy part, and afterwards the smaller, until he comes to grains, which he examines with the greatest care, on account of the diamonds. As soon as a negro has found one, he must make it known by clapping his hands, and the surveyor, who is seated on an elevated chair, so that f he can oversee the work, takes and de- posits it in a dish filled with water, in which all those found during the day are collected. They are then de- livered over to the superintendent, who counts and weighs them, and enters the result, with other particulars, in a book kept for that purpose : he keeps them in a bag until he delivers them, which he does twice a week, to the gov- ernment at Tejuco. Every superintendent has to live in the neighborhood of the principal washing-establishments, which were formerly leased for a certain sum by the government ; but the im- 192 A POPULAR TREATISE ON GEMS. positions practised were so great, that it took the super- intendence upon its own account in 1722, and has guarded the diamond districts along their lines by strong sentinels, who will not allow strangers to pass through .without the permission of the general superintendent; and even the inhabitants, when crossing the line of the diamond districts, have to procure written permissions from the above au- thority ; and everybody must, on leaving the district, submit to a personal and strict examination and search by the soldiers ; foot-passengers are always arrested by sen- tinels and spies continually on the alert. St. Antonio de Tejuco, forty leagues from Villa Rica, is the capital of the diamond district, and the seat of the superintendence of the Junta Diamontina, consisting besides of a confiskal, two cashiers, one inspector-general, and a book-keeper. Ail the diamonds procured are delivered up yearly to the government at Rio Janeiro. From four to five thousand negroes were engaged in the years 1772 to 1775; in the year 1818 but one thousand : among them were the feitores or surveyors, one hundred in number, in the latter year ; likewise ten superintendents, whose business it is to conduct the mining department and the collection of the diamonds. In order to encourage the negroes, presents of tobacco, cloth, &c., are awarded, according to the price of the dia- monds which they find ; the one who finds, for instance, an eighth (seventeen carats and two grains) receives his entire liberty ; they are severely punished for any offence, and if repeated are not allowed to be at this work. Notwithstand- ing the most rigorous regulations and the most watchful attention of all the officers, the frauds in stolen diamonds are very considerable ; and it is estimated that the smuggling amounts to one third of the whole income*. The smugglers, who are runaway slaves, examine the most remote parts of DIAMOND. 193 the district, or steal the diamonds at night from the work- ing establishments ; others, again, who understand it, will take the stolen diamonds from the negroes, and devise means of escaping with them, either in the soles of their boots, or in hollow canes, &c. ; and it is a remarkable feet, that all diamonds obtained from the smugglers are inva- riably larger and more beautiful than those which axe brought into market by the government. The thieves practise all manner of tricks and impositions, even in the presence of the surveyors : for instance, they conceal the good diamonds, during the washing hours, between the fingers, the toes, in the ears, in the mouth, or in the hair ; they also throw them away with other stones, in order to pick them up in the night ; they often even swallow them. The soldier who arrests any smuggler, receives a reward ; the property of the latter is confiscated, and he is sent to Angola as a prisoner, for upwards of ten years. The pure transparent diamond, which is cut in the differ- ent forms already mentioned, loses generally one third to one half of its original weight by this operation. The following table shows the original weight of the rough diamonds, and that after being cut ; viz, : Regent, when rough, weighed 410 carats, and when cut, 136 u /ie carats. Grand Mogul, " " 780 1 /., " " 279 /i " Ko-M-noor, " " ~186/a " " 82"/ 16 " South Star, " " 254'/a " " 124/i . " Nassak, once cut, 89 3 /4 " " 78 10 /i " It will be perceived, therefore, that the skill of the dia- mond-cutter has made great progress in modern times, in- asmuch as the weight of the Ko-hi-noor and South Star was only reduced to one half of the original weight. In purchasing rough diamonds, every precaution ought to be used to prevent getting false diamonds instead of 9 194 A POPULAR TREATISE ON GEMS. real ones, and faulty ones instead of pure diamonds. The officers of the Junta Diamontina test the rough stones by holding them whilst rubbing together, close to the ear, and listening to the tone produced, which gives them ample satisfaction of their being genuine, as it is only to be ob- served in real diamonds. It requires, however, consider- able practice to distinguish them with accuracy by this test. Strangers particularly, are imposed upon by the negroes in Brazil, by purchasing from them gems cut and polished with the facets, resembling those of the diamond; and although any one acquainted with the diamond will soon detect the imposition by the want of specific weight, the peculiar lustre, fire, and hardness, he requires to be on his guard. If, however, the diamond is ascertained to be genuine, we have to examine particularly its purity, color, form, and size, these being the qualities by which the price of a rough diamond is to be determined. It requires considerable experience to determine from a rough diamond whether any of its faults are at the surface or in the interior, whereby often the diamond, in removing all its faults, may be diminished to half its size. We often, however, judge the rough stones by their color ; those turning towards the green color are considered to be the best ; those of a reddish color to be good stones ; the black color indicates a hard stone ; and we judge a yellowish or grayish color as making bad diamonds. The natural form of a diamond, likewise, gives a characteristic to the pur- chaser of rough stones ; for a flat, thin, or triangular stone would lose much in the grinding, and not be so high as to give it sufficient fire ; and likewise we are not sure of the result of the cutting, and the hemitrope crystals are very difficult to work. The best forms of diamonds for cutting are the octahedron, which is principally found in the East Indies, and is called Pint by the diamond-grinders ; and the DIAMOND. 195 rhombic dodecahedron, which is found principally in Brazil : cheese-stones is the name given to amorphous diamonds b} the diamond-grinders. According to the quality of the diamonds, they are divided in Sumbhulpur into four classes, which correspond with the deities of the Hindoos the Bramins, Tschettri, Wassiers (Bysh), and Tschadrie. The native jewellers are very expert in estimating the value of these diamonds. The value of the polished diamonds depends on the fofc lowing conditions : 1st. Color. The limpid diamonds command the high- est price, and twice as much as those that are colored; the blackish, brownish, yellowish, brown, steel-gray, and impure bluish ones, stand in no value, and are often rejected for working. 2d. Purity, Faultlessness, and Transparency. The Dia- monds ought to be, according to the technical terms of the jewellers, free from ashes, gray spots, rusty or knotty places, veins, fissures, scratches, feathers, flaws, sand, grains, and faint yellow or vitreous spots. The Brazilian diamonds exhibit sometimes, in their interior, designs resembling mosses, like those of the Mocha stones and agates ; and we may often observe it in the green diamond ; if a limpid diamond plays somewhat in the brown* color, it is called shrugging, and this diminishes its value : paunched, are those diamonds which are neither pure nor clear. The transparency and clearness of the diamond are di- vided into three degrees, viz : A, of the first water, as in those diamonds which are free from even the slightest faults, and stand highest in price. B, of the second water, as in those diamonds which, although clear and limpid, are marred by some dark spots, clouds, or flaws. C, of the third water, as in those diamonds having ?. 196 A POPULAR TREATISE ON GEMS, t gray,' brown, yellow, green, Hue, or blackish color ; or those that are limpid, but are injured by several material faults. In order to determine accurately the nature of diamonds, it is well to breathe on them, whereby they lose for a mo- ment their lustre, and the ,eye is then better enabled to examine them and distinguish their faults. The real dia- mond becomes clear much sooner than the false. 3d. The Cut. The perfect and regular cut of the dia- mond increases its value considerably; a brilliant, -for in- stance, of one carat, is worth twice as much as a rough diamond of equal weight. It depends upon the proportions of the height to the circumference of the diamond, and that the planes and facets stand in a regular proportion, for should this not be the case, the diamond would lose much of its fire. Likewise, the form of the diamond influences the price. A brilliant is dearer than a rose-diamond, and this again is dearer than the thick and table-stone. The facets of the brilliant also influence the price : once cut is a brilliant that possesses no cross-facets on the lower part of the stone ; twice cut, there is one row of facets on the collet side; thrice cut, the brilliant possesses the facets on the bizel and collet side, according to the rule of cutting. The more rows of facets a brilliant displays, the higher price is put upon it. 4th. The Size and Weight. The price of a diamond de- pends considerably upon- its size ; those diamonds which are of great splendor and size are called Paragons' or Non- pareils, the Ne Plus Ultra; the less weighty ones are valued according to their actual weight. The weight em- ployed in Sumbhulpur is the rutta and masha. Seven rutts is equal to one mash, and one rutt is equal to two grains. In Brazil the weight is specified by carats (quilates). Seventeen and a half quilates are equal to one drachm (oc- DIAMOND. 197 tava) ; thirty-two vintenes are equal to seventy grains (graos) ; one carat is equal to four grains. The price of diamonds is determined in trade by exam- ining accurately their character as above stated, and then the price is fixed ; the weight of the diamond is at first multiplied by itself, and the sum obtained multiplied again by the price of one carat. A brilliant, for instance, would weigh two carats, and on examining its properties, if good, its price would be found to be forty-four francs. We pro- ceed in the following manner to get at the full value of the diamond : 2X2X44 = 176 francs. We do not always, how- ever, arrive at the correct result. If the brilliants are very large, and exceed the weight of eight or ten carats, it is difficult to arrive at a standard. I will endeavor to give below a table of the prices of the diamond in Holland, France, England, Germany, and .the United States, as far* as ascertained, and as near to the actual price current as I could obtain. Rough diamonds fit for cutting are worth ten or twelve francs per carat ; any diamond exceeding the weight of one carat is estimated by the square of its weight multiplied by eleven or twelve francs as the average price. Eose-diamonds of first water and one carat, " second " 20 francs. 18 " 14 " Brilliants, 30 to 35 pieces to* the carat, - * " 20 " " " - U JQ U U U m 5 " " " - 4 _ 22 " 40 " 88 35 " 36 " Brilliants of three grains are in much demand, and are worth fifty francs per carat. Those of three carats, used for icentre-pieces in necklaces, are sometimes worth four hundred francs. Rose-diamonds for mounting, and forty 198 A POPULAR TREATISE ON GEMS. to the carat, are worth twenty francs the carat ; if r* little larger, thirty-live francs per carat. Diamonds unfit for cutting, and used by glass-cutters or glaziers, are worth from ten to fifteen francs per carat, and still smaller ones are worth less ; they are now employed by lithographers for their engravings and etchings. In 1837, according to Ketot, Pujoux, and Lucas, the price of diamonds of the first water was three hundred francs per carat ; and second water, one hundred and fifty, Diamonds of one 'grain and less, The double cut, first water, 6 to a grain, Of two grains, - Of three grains, - Of one carat, - A diamond of 6 grains, 10 12 15 18 '* of 6 carats, 96 francs per carat. 125 " 150 " 170 " - 200 260-280 ( - 600 ' - 1000 - 1400 - 1800 - 2400 - 3500 - 5000 The abqve prices are from Brard's Mineralogie appliquee aux Arts. . ' The price of diamonds (in 1855), according to Mr. Achard, a celebrated dealer in Paris : Glass-cutters' diamonds, less than a grain, 50 francs, or $10 00 per carat. Diamonds to reduce to powder, - - 12 " 2-50 " These are the natural diamonds. Diamond powder for polishing, Compact diamond, called carbonite, " in powder, Diamonds of 1 carat are worth - " 2 " " 8 francs, or $1 75 per carat. 4-6 " 1 50 " 6 " 1 '50 " 250 francs, or $50 00 800 " 160 00 - 1,500 " SOO'OO - 10,000 " 2000 00 DIAMOND. 199 According toBarbot, the present (1858) price current of diamonds of good quality, and in relation to their weight and various forms, is the following : A diamond of 1 carat is worth, per carat, 300 francs, or $60 00 8 grains recut, 8 to the carat, s-, from a, not ; pcd, to intoxicate. As re- gards the color, Pliny says : "ad riciniam crystalli descen- det albicante purpurae defectu," purple gradually fading into white. This is not, however, the only amethyst of the ancients ; the violet-colored sapphire, the violet fluor spar, (" sculptaris faciles," easily graven Pliny,) and some other purple' species were designated by the same name. It has also been supposed that 'garnet came under the same de- nomination. This name occurs in Scripture, being that of the ninth stone in order on the high priest's breast plate of judgment, with the name Issachar engraved thereon. Amethysts were always used for engraving. The bust of Trajan, in the Royal Library, at Paris, and the Apollo Belvidere, the Farnese Hercules, and the group of the Lao- coon, are splendid specimens of it. It occurs massive in boulders, or in hexahedral prismatic crystals, terminated by hexahedral pyramids. Its crystals are rarely as distinct as those of quartz, being, for the most part, latterly aggre- AMETHYST. 267 gated by the whole prism, the terminal pyramids alone being separated from each other ; its fracture is from con- choidal to splintry ; it is transparent to translucent; of a vitreous lustre ; color of a high and dark violet blue, and from its richest tinge to almost colorless, in one and the same specimen. It scratches white glass, gives fire with steel, but yields to the file. Its specific gravity, 2-75 ; be- comes electric by rubbing, which lasts, however, but half an hour. Before the blowpipe it loses its color. Its com- ponent parts are pure quartz, colored by manganese and iron. It occurs in veins of the older formations, studding the interior of agate balls or geodes in tho amygdaloid and trap rocks of Hungary, Silesia, Saxony, Tyrol, Oberstein ; and as boulders of splendid specimens in Ceylon, Siberia, and Brazil. It is wrought in the same manner as rock crystal, being cut on a copper wheel with emery, and pol- lished on a tin plate with rotten stone. In order to raise its lustre, many facets, and very frequently those of a rose- diamond, are given to it in cutting. It is sometimes cut in" the form of a brilliant, and when set is supplied with a blue or red foil, provided the amethyst is pale, for the deep- colored ones do not require any artificial assistance. It is used in almost every description of jewelry, such as rings, ear-rings, and breastpins ; but it is set in necklaces to the best advantage, and is the only colored gem which may be worn with mourning, an advantage which adds 'to its value. The amethyst is no longer held in such estimation as formerly, but the color, when intense and uniform, as also the size, contribute greatly to its value ; and good well-cut amethysts, of one carat, are worth from three to five dollars, and so on, in proportion to their size ; an amethyst fifteen lines long and eleven lines broad, ex- quisitely fine, was valued at five hundred dollars. The best amethysts now in commerce come from Cey- 268 A POPULAR TREATISE ON GEMS. Ion, Siberia, and Brazil; the first are commonly called Oriental amethysts, which, however, must be carefully distinguished from a much more valuable gem, the true Oriental amethyst, which is the violet .sapphire. I have in my collection a quantity of the Brazilian amethysts, which are of an intense violet color, and of a very large size. Amethysts occur also at Pic Bay, and at Gorgontwa, Lake Superior, crystallized in trap ; also at Bristol, Rhode Island, and occasionally throughout the trap region of Massachusetts and Connecticut. The amethyst, is valued by the jeweller in proportion to the dcpth r richness, and uniformity of its color, and its perfect transparency ;; it . forms, then, a stone of ex- quisite beauty, its color being, perhaps, more generally attractive than that of any other gem, especially as it may be obtained of as large a size as can be conveniently worn. It is worn by priests, bishops, and pontifical dignitaries- as a ring-stone set with brilliants. Like many other stones, it is less brilliant by candle-light, and it appears at all times to best advantage when surrounded with pearls and set in gold. Amethyst has lately been employed by the cameo-cutters of Paris, for cameos and intaglios ; the head is cut at the collet, which is the thick part of the stone, and the crown having diamond facets produces a fine effect. The amethyst is often imitated by fluor spar or violet- blue lime spar; both, however, are softer than amethyst ; the liine is lighter, and the fluor is heavier than amethyst. But it is imitated very strikingly by pastes, so that with great difficulty the real is to be distinguished from the imitation; the latter, however, is somewhat heavier, on ac- count of the metallic oxides contained in the composition* The following is the best receipt for imitating the amethyst : COMMON QUARTZ. 2G9 1000 parts of strass, 8 " oxide of manganese, 0'2 " purple of cassius, and .500 " oxide of cobalt, One of the largest geodes of amethyst was brought into England in 1819, weighing one hundred ami fifty pounds; it was two feet long and fourteen inches' broad, and con- tained most magnificent crystals, of the deepest violet color. On account of having been set down at too low a price at the custom-house, which was sixty-five pounds sterling, it was confiscated. COMMON QUARTZ. But a few varieties of the common quartz are used in jewelry, which are : the Rose Quartz, the Oafs-eye, the Prase, and the Avanturine, Rose Quartz, This mineral generally occurs massive; it is semi-trans- parent, and translucent on the edges ; has a vitreous lustre ; conchoidal and splintry fracture ; is of a rose-red color ; some- times giving a lustre of mother-of-pearl. It scratches glass; has a specific gravity of 2*64 to 2*67; its color, which is derived from the oxide of manganese, becomes paler before the blowpipe. Rose quartz occurs in gangues of granite and gneiss, par- ticularly fine in Sweden, Bavaria, Bohemia, and Siberia ; also a beautiful dark color in New-Hampshire and Massa- chusetts. Rose quartz is cut and polished for jewelry ; such as rings, breastpins, and snuff-boxes; it is cut on a copper wheel with emery, and is polished with rotten, stone and putty, on a tin plate, receiving the form of a cabochon or 270 A POPULAR TREATISE ON GEMS. table, and when set requires a foil, colored by carmine or solution of gold, as it fades when exposed a long time to the light. The rose quartz is not held in great estimation ; the color as well as the lustre of faded rose quartz may be resuscitated by being left for some time in a moist place. A vase of rose quartz was in the possession of the Marquis de Dree, nine inches high and two inches in diameter. Cat's-eye. The name of this mineral is derived from the peculiar play of light perceptible on its surface, by which it resem- bles the rays of light in the eyes of a cat ; it is not ascer- tained whether the ancients knew this mineral, and whether it was comprised in their .asterias; but it is well known that cat's-eye is in high estimation among the Malabars and Moors ; and it is worn throughout the whole East, where it is employed as an amulet, being believed to possess the virtue of enriching the wearer. Cat's-eye occurs massive, and in more or less roundish pieces ; has a. conchoidal fracture ; is translucent and trans- parent sometimes on one end ; it has a shining lustre, between vitreous and resinous ; gray and brown, green, red and yellow color ; it presents a peculiar floating light, which is particularly visible if cut in high cabochon, as it usually is when brought to market; it scratches glass; has a specific gravity of 2'56 to 2'73, and contains 95 silex, 1*75 alumina, 1'50 lime, and 0*26 oxide of iron. In many specimens, there may be observed small parallel white fibres, which are supposed to be the cause of its peculiar play of light ; but the semi-transparent varieties, which are equally chatoyant as the more opaque ones, present no such appearance. This leads to the conclusion that COMMON QUARTZ. 27l amianthus in its finest fibres occasions the phenomenon, and the chemical analysis of the latter corresponds with the additional constituents of the cat's-eye. By exposure to a strong heat, it loses its lustre and transparency ; and, in' small fragments, is fusible before the blowpipe. Cat's- eye is found in fragments of gangues and boulders, of very small size, never larger than a hazel-nut, in Ceylon, on the coast of Malabar, in the Hartz mountains, Bavaria, and in this country, (in Vermont, New-York, 50 " brass powder. The artificial avanturine, as made in Italy, is a silicious oxide of copper. The mode of manufacturing the best quality, which is done very extensively in Italy and France, is still kept a secret ; that the copper is reduced first to a sub-oxide, and nearly to its crystalline metallic state, may be inferred on examining with a microscope the common artificial stone, which has a most splendid appearance* The best ananturine is manufactured in Venice, by M. P. Bibaglia, who alone appears to have the secret of excelling the natural stone. Messrs. Fremy and Ckmendot, expert French chemists, have succeeded in approximating the Ve- netian manufacture, by heating 300 parts ground glass with 40 parts of protoxide of copper and 80 parts of oxide of iron, and allowing the mass to cool very slow. Large blocks of the factitious avanturine, with a great variety of manufactured ornaments, were admired in the Paris Exhibition, in 1855. JASPER. This mineral is of Oriental origin, and is very often men- tioned in the Bible. * It was the sixth stone in the plate of 12* 274 A POPULAR TREATISE ON GEMS. the high-priest. Jasper was well known to the Greeks and Romans, and according to Pliny, who has described sev- eral varieties, the best came from Scythia, Cypria, and Egypt, on the banks of the Nile. The lapidaries formerly made use of it in their works, particularly the Egyptian jasper, which afforded them abundant material. The col- umn of Memnon and the foundation of the column of Pom- pey were constructed of it, and we find daily, among the excavations of Herculaneum and Pompeii, fragments of ruins, composed of Egyptian jasper. Jasper occurs in enormous masses ; has a conchoidal frac- ture ; is opaque ; its lustre is slightly resinous, like wax, often dull ; it is of white, red, yellow, green, blue, brown and black colors ; it scratches glass, but yields to rock crystal ; its specific gravity is 2-31 to 2*67. It is usually found in gangues, seldom in strata, in Egypt, Bohemia, Saxony, Tyrol, Hungary, France, Italy, Spain, Siberia, Corsica ; in the United States, principally in Florida, North Carolina, Massachusetts, &c. ; also, in Nova Scotia. A fine yellow jasper is found at Vourla, bay^of Smyrna, in a low ridge of limestone, to the right of the watering- place, between the harbor and the high hills that commence their rise about a mile back ; it is here associated with a beautiful opal, coarse carnelians, chrysoprase, and horn- stone, and these minerals seem to occupy in the limestone the place of the hornstone, which is found in various parts of the adjoining country, and also at Napoli di Romania, in Greece. The plains of Argos are strewed with pebbles of red Jasper. The jasper and quartz rocks of Siberia am well known materials of extreme hardness, worked only in the Russian empire, and are rarely met with, except as imperial pres- ents to princes and distinguished foreigners. A group of JASPER. 2*75 very remarkable objects was exhibited among the Russian goods in the London Exhibition. The material of some of these vases is quartz rock, but most are of a kind of pseudo jasper or pseudo jasper lava, of greenish color, and extreme toughness and hardness, resisting almost every tool, and requiring to be cut with emery, like the hardest gems. These rocks chiefly exist in Siberia, beyond the Oural, and are in great abundance and variety. The vases of jasper were worked at the imperial manufactories of Ekaterinen- burg and Kolyvan. There almost the whole work is per- formed by manual labor ; the only machine used is a simple lathe, on which the object to be turned is placed, and worked by iron tools and emery. No tool will touch these stones, both chisels and files of the hardest temper turning without producing any effect. The time 'for furnishing vases of considerable magnitude is often many years, and their value is calculated by the cost of the large establish- ment kept at constant work. A large vase, measuring three feet on each side, in a square form, was exhibited, hollow under the rim, with foliage in the same, and was one of the great curiosities in the Exhibition. Smaller vases, an olive- green jasper urn, decorated' with admirably worked foliage in relief, from the imperial manufactories, were -likewise exhibited, all of which excited the admiration of the specta- tors; and since the times of the Greeks and Romans no such gigantic works, both in dimensions and weight, have been wrought. The quantity of intaglios and cameos from the" ancient Greeks and Romans is too numerous for giving them a space in this treatise, for it would fill a whole book to spe- cify the antiques which are scattered around the world, in the various museums of Rome, Vienna, Paris, London, Ber- lin, Dresden, and the private cabinets which have for centu- ries existed in noble families. According to their varieties, which are very numerous 276 A POPULAR TREATISE ON GfEMS. that is, in color and structure they receive their names \ but they may still be classified into the following two- divisions : 1. Egyptian Jasper, (Egyptian pebble,) which occurs- in spheroidal pieces,, of a gray-brown and red color, the- form of which is cut and polished in annular represen- tations around its centre. It is found in Baden, tip- per Egypt, and other places ; among the pebbles of the river Nile it is frequently discovered ; and in the year 1714, it was found near the village of Inch eric; by Paul Lucas. 2. Ribbon or Striped Spar. It occurs in masses, with nearly conchoidal fracture, around which parallel, straight,. or twisted stripes of a gray, green, yellow, red, or brown color may be perceived ; it is principally found in Siberia, the East Indies, Corsica, Tyrol, and the Hartz mountains ; some of the West India islands produce most splendid spe- cimens. Jasper is principally used for seals, snuff-boxes, vases, table-plates, and for some architectural purposes. When in lumps, it is divided by means of copper saws and fine sand, and then cut on copper or leaden wheels with emtfry, and polished on tin plates with rotten stone, colcothar, or charcoal ; or it may first be polished on wood with pumice stone, and lastly on a tin plate with rotten stone and water. The yellow jasper is often employed in mosaic works in Italy, and the striped jasper as cameos. Jasper- has no great value in trad-e, unless it be of exquisite quality, and fine objects be made of it. It generally commands the best price in China, where the emperor has a. seal cut of it. A vase of red Jasper, with white veins, and one of black jasper, with yellow veins, may be seen in the Vati- can. Chatouilles and other boxes of considerable size CHALCEBONt, are frequently fotmd in the jewelry stores of France, Eng- land,- and the United States, HORNSTONE, Hornstone occurs massive, globular, stalactiform, and in pseudo-morphous crystals of carbonate of lime, and also in the form of petrified wood, (wood-stone or agatized wood.) Its fracture is either conchoidal or splintry ; it is opaque or transparent on the edges; has a dull or shining lustre;- deep gray, brown, red, yellow, or green, and rarely a pure color. Often it has several colors in one and the same specimen, such as points, spots, and stripes. It scratches glass, and has a specific gravity of 2 '53 to 2 '65. It is mostly found in the gangues of the older formation J also in the old red sandstones and alluvial formations, in Bohemia, Saxony, Sweden, Siberia, Hungary, and a number of other places ; in the old red sandstone of Thuringia. I have traced one stem of the red agatized wood eighteen feet in length and two feet in diameter. The price of hornstone is very low ; it is used for snuff-boxes, seals, crosses, mortars, and principally as knife and fork handles. It is now used by silversmiths to mount butter and dessert knives and forks," which are imported from Germany in considerable quan- tities-. CHALCEDONY. This mineral was held in great estimation by the ancients, who received their principal supplies from Egypt and other parts of Africa. In Rome, much use was made of it for cameos, many of which may yet be seen in collections. The inhabitants of Iceland are likewise said to value it very highly, and to attribute many medicinal properties to it* 278 A POPULAR TREATISE ON GEMS. It is found in crystals, such as cubes, but mostly massive, botryoidal, stalactiform, globular, or reniform, &c. The fracture is even, sometimes running into conchoidal or splintry ; it is semi-transparent or translucent, of little lustre, or dull ; of white, gray, blue, yellow, brown or green colors, which are all of a light shade, and variously figured, striped, spotted, &c. It scratches white glass, and has a specific gravity of 2'58 to 2*66. It is distinguished into the following varieties, viz. : 1. Chalcedony proper, or chalcedony x, wherein white and gray stripes alternate with each other. 2. Mocha, or tree stones, are such chalcedonies as display black, brown, or red dendritical figures, 3. Rainbow, or agate chalcedony, is chalcedony of thin and concentric structure, which, cut across and kept towards the light, displays an iridescence. 4. Cloudy chalcedony, has a light gray and transparent base, with dark and cloudy spots. 5. Plasma, dark grass-green. This mineral was very often employed by the ancients for cutting. 6. Semi-carnelian, or ceregat, is generally called the yellow chalcedony. 7. Sappharine, is the sky or sapphire blue chalcedony. 8. St. Stephen's stones, is the white chalcedony, with blood-red spots. There are many more varieties, and in my own collection I have polished chalcedonies, among which, perhaps, as many again may be enumerated. Chalcedony was originally procured from Chalcedon, in Asia Minor, whence its name. Chalcedony is found in gangues, and in the cavities of many rocks ; also in boulders and pebbles. Localities exist in Saxony, Hungary, Faroe Islands, Ceylon', on the shores 279 of the Nile, in Nubia, Nova Scotia, the UnUed States, (in Connecticut, Massachusetts, Pennsylvania, Ohio, New-Jersey,. Missouri, Florida,) and in other countries; but the best specimens are brought from Oberstein, Iceland, and the Faroe Islands. The finest specimens are employed in jewelry, for rings, pins, bracelets, necklaces, and seals; -the more common for snuff-boxes, vases, buttons, &c. The larger masses are cut by means of a copper wire, with emery and oil on a copper wheel ; they are polished on a tin plate with rotten stone, putty-powder, and pumice stone. The cutting is generally done on a large scale, like that of agate. Many are suscepti- ble of receiving figures artificially, by means of the nitrate of silver. By Oriental chalcedony is generally understood the better qualities ; those chalcedonies of two or three divisions, called onyx, are used for cameos. The value of the chalcedony depends on its quality, such as purity, color, and the figures and drawings displayed on it ; and among all the varieties of chalcedony, the mocha stone stands the highest in price, and also the onyx, which is principally employed for cutting cameos, and according to its size, commands a high or low price. Mocha stones are sold in France at from five to eight francs. The cabi- net of Dresden contains a plate of onyx, about three inches broad and long, which is estimated at twenty-five thousand dollars. CARNELIAff. This stone was known to the ancients by the name of Sarda ; which, according to some, is derived from a place in Lybia or Sardinia, or, according to others, from the Arabic word sarda, meaning yellow; it has been employed very frequently for cutting intaglios or bas-relief gems. Carnelian occurs massive or in pebbles ; its fracture is con- 280 A POPULAR TREATISE ON choidal ; lustre resinous ; it is semi-transparent and translu- cent; of a blood-red, yellow-brown, or yellow color; fre* quently dark at the outside* growing paler towards the in- side ; the colors are sometimes changing striated ;- it scratches white glass, and has a specific gravity of 2-59 to 2 '63. There are two varieties known by lapidaries and jewellers which are better than the others; those having a pale color or yel- lowish tinge, and those having a dark-red color; the latter are in the highest estimation, and are called by the French cornalines de vieille roche. Sardonyx is called a carnelian, having as its principal color tne dark-brown or orange-yellow, interchanged with layers of a white color. Carnelian onyx has a blood-red base, marked with white stripes. The finest carnelians come from Siberia, India, Arabia, Nubia, Surinam, Oberstein in Germany, and Tyrol ; they occur mostly as pebbles or in .cavities of^ rocks. In the United States they are found on Lake Superior in large quantities, in Missouri, and in Massachusetts. The carne- lian is used for numerous articles in jewelry, such as seals, rings, watch-keys, &c. ; it is cut on a leaden plate with emery, and is polished on wood with pumice stone, and ob- tains its highest polish on a plate composed of lead and tin with rotten stone and water. The form of its cutting is that of pavilion or step cut, on the upper part, and either quadrangular, hexagonal, octangular, or round ; and for raising its lustre or color it is furnished with a, silver or gold foil, or with red paint on its base. The color of th carnelian is also improved by calcination ; the yellowish kind, for instance, by calcining it in a moderate heat and cooling.it slowly, may assume a good red color. It is said that the ancients boiled the carnelian in honey in order to heighten its- color. Colored figures or drawings may suc- cessfully be represented by a mixture of white-lead, colco- CARNELIAN. 281 thar, or other metallic oxides, and gum-water, which is the material for drawing on it, and by burning the same under a muffle. Carnelian is divided into Oriental and occidental ; the first is found in the old rocks, and is generally very hard, rich in color, clear and transparent, and takes a high polish, is brought from Surat, in the Indies, and valued at ten francs the kilogramme ; the occidental carnelian is softer, of a yellower red and less brilliant. Stygmite is a beautiful variety with variegated colors, of reddish-yellow or yellowish-red, with many white lines pass- ing through the stones. The ancients, particularly the Romans, were very partial to engraving on carnelian, and some very remarkable stones are still in existence in the imperial library at Paris. The seal of Michael Angelo, which is valued at 50,000 francs, is said to have been engraved by Maria de Descias after the original of Praxiteles ; the bust of Ulysses, Hercules killing Diomede, Jupiter, Mars, and Mercury. The great scarabee in carnelian, in the Prussian cabinet, which represents the five heroes of Thebes, is a master-piece of Etruscan art. The crown jewels of France contain some very costly car- nelian engravings of very large size. The faults of the carnelian are fissures, unequal color, and flaws from other stones. Carnelian is, on account of its being less brittle, more useful for engraving and cutting cameos ; the white layers are generally used for the figures of cameos and' the red for the base. Sometimes such carnelians as are cut with bas-relief objects, are filled out with colored strass ; and we receive from India, very fre- quently, cameos with the most singular drawings, and which are made by the inhabitants in the following manner : the whole carnelian is covered with carbonate of soda, and then 282 A POPULAR TREATISE ON GEMS. exposed to the fire for a few minutes, whereby a strass is formed, upon which the figures are cut. The value of car- nelian is much higher than chalcedony, but yet depends on all its qualities of color, transparency, equal division of color, and freedom from faults, such as fissures, clouds, dark spots, &c. For a perfect sardonix, a very high price is generally given, particularly when the layers are very distinct and run quite parallel, and are pretty thick, so that they are fit for cutting cameos or intaglios. The blood-red is second in value, and the pale-red third ; but the cheapest are the yellowish, brownish, or whitish kinds ; the prices vary from twenty dollars to twenty cents per piece. There exists a cameo of sardonyx, representing the portrait of the celebrated Father Fontanarosa, having his face white, with the base, cap, and cloak black, so that it may distinctly show the Dominican monk. HELIOTROPE, BLOODSTONE. This stone derives its name from the Greek language, having been used in ancient times for observing the sun. Pliny speaks of heliotrope. It occurs in massive and obtuse angular lumps, of a conchoidal fracture, is trans- lucent on the edges, of a resinous lustre, and leek-green color, with red and yellow spots. It scratches white glass ; has a specific gravity of 2*61 to 2'63. Heliotrope is found among amygdaloid, in Tyrol, in the United States, (in New-York, near Troy,) Scottish Islands, Siberia, Faroe Islands, Egypt, Barbary, Tartary, &c. It is principally employed in rings and seals, watch-keys, snuff-boxes, and other articles of jewelry, also for sword and dagger han- dles ; and is wrought like chalcedony, but sometimes cut on brass plates ; its forms are various : as cabochon and pavilion. AGATE. 283 Heliotrope has been greatly admired in modern times ; its pric'e depends upon the color and quantity of red spots contained in ft. From one to twenty dollars is the usual price for good and large specimens. It is said that superstitious people in the middle ages valued the heliotrope, with many red spots, very highly, thinking that Christ's blood was diffused through the stone. AGATE. This stone was well known to the ancients, under the name of achates, and was used for various purposes of jew- elry. In Rome, it was principally used for cutting cameos from the striped kind, the onyx. It has also been worn as an amulet, with different characters engraved upon it. Its name is derived from a river in Sicily, where the ancients procured it. Agate is a mixture of several species of quartz, which are variously combined ; chalcedony or carnelian usually forms the principal part, and is mixed with horn- stone, jasper, amethyst, quartz, heliotrope, cachelong, and flint; and according to the predominating substances, it is sometimes called chalcedony, jasper, or carnelian agate. Its color, as well as its other characters, depends upon the na- ture of the mixed parts ; likewise its hardness ; but it usually scratches white glass, and has a specific gravity of 2*58 to 2-66 at the utmost. According to the different figures represented in agate, it receives its various names. 1st. Ribbon, or striped agate, representing layers vari- ously colored, and alternating with one another. Onyx, or agate onyx, are such agates as have the colors beautiful and distinct, and whose layers run in a parallel direction with the larger surface ; whereas the common ribbon agates display their various layers on the surface, without being 284 A POPULAR TREATISE ON GEMS. parallel. If the stripes run together around the centre, it is called the circle agate, and if in the same stone the centre shows more colored spots, it is called the eye agate, or eyes tone. 2d. Fortification agate is that brownish agate, the vari- ous colored stripes of which run in a zig-zag, or irregular lines and angles, representing the ground plan of fortifica- tions. 3d. Rainbow agate ; the curved stripes have the property of displaying rainbow colors when held towards the sun, or candle-light, and the more distinctly if the stone is cut very thin. 4th. The cloud, landscape, dendritic, figure, moss, punc- tated, star, petrifaction, shell, coral, tube, fragment, and ruin agates are all the various forms in -which the agate is dis- played, according to its figure or drawing. A ruin or frag- ment agate may be pasted together from the fragments of a common ribbon agate, so as to make it represent old walls, whereby it receives the name of breccia agate ; some- times the rainbow agate occurs in connection with the shell agate, where the moss surrounding the petrified shells forms the rainbow agate. The royal collection at Dresden contains a table service of German agate; at Vienna, in the imperial cabinet, there .is an oval dish twenty-two inches in length, formed from a sin- gle stone. The achates of the Greeks were so called from the river Achates, in Sicily, whence, according .to Theophrastus, these stones were originally brought. J asp achates corresponds to our jasper agate ; sardachates contained layers of the sarda, or carnelian ; dendrachtes, from &evtpov, a tree, corresponding to our moss agate ; hsemachates, from d^a, blood, which was an agate sprinkled with spots of red jasper. AGATE. 285 Among the crown-jewels of France, is a very valuable set >f agates, ten cups and sa.ucers, four urns, four chandeliers, four busts, two ewers, two basins, two vases, two bowls, two salvers, one decanter, and one candlestick ; the whole set is valued at 500,000 francs. At the French Exhibition in 1855, a magnificent Oriental agate, by Froraent Maurice, belonging to the Princess Mathilde, was exhibited, having the engravings of the three infatuations, the amorous, the poetical and sad, most tastefully represented. It is the Benvenuto Cellini of our day. The most celebrated cameo in Oriental agate, is the bust of Alexander the Great, which is a perfect gem ; the head is quite independent in color froin the base of the stone, and the execution without a blemish. The Orleans collection contained two agates : one repre- senting the death, of Cleopatra, as a half-body ; the other, Lysimachus, the head girdled with a diadem. A large black agate, particularly remarkable for its perfec- tion and .the complication of its workmanship, repre- sented a captive followed by two generals on horseback, and several other persons, one showing a trophy, and another a laurel branch, An intaglio of Neptune, belonging to the Sabatini Museum, was also exhibited. Agate is found in gangues, in gneiss, porphyry, or amyg- daloid ; also, as boulders and pebbles, in rivers, &c. It is found in Baden, Oberstein, Saxony, Bohemia, Hungary, the Faroe Islands, Siberia, the West Indies, and in the United States, (Massachusetts, Rhode Island, New Jersey, Indiana, Missouri, Maryland, Georgia.) Those occurring- in amygdaloid are mostly in the form of geodes, or balls, hollow inside, and coated with quartz or amethyst ; when the rock begins to disintegrate, these balls, becoming 286 A POPULAR TREATISE ON GEMS. loose , fall scattering around the soil, and are then collected by persons who make a business of either selling or cutting* them. The agate is used not only for various purposes of jewelry and ornaments, such as seals, snuff-boxes, crosses, cases of various descriptions, ear-drops, &c., but also for numerous other useful purposes, on a large scale ; such as slabs, mortars, vases, instruments, knife and fork handles, playballs, &c. The manufacturing of th^m forms a con- siderable branch of industry in a part of Germany. The agate, after having been reduced to suitable sized pieces, by means of a saw, chisel or hammer, is then cut on a copper wheel by means of emery, powdered garnet or topaz, and is afterwards polished on a tin plate with rotten stone, putty or pumice stone. Oberstein, a small place in 'Rhenish Bavaria, in the north of Germany, has five large manufacturing establishments for the sole purpose of cutting and polishing the common gems or semi-precious stones, and it is the only place where this branch of business is carried to any great extent. Twenty mills are constantly driven by water, and more than one hundred thousand dollars worth of work is turned out yearly for export ; a sum which is small in comparison with the enormous quantity of goods manufactured and set afloat, but pretty considerable for such places, where labor is so cheap, and the best of workmen may be had for one dollar and fifty cents per week. At Oberstein the business is divided into two branches; the one is devoted to the cutting and polishing of the agate, and the other to the boring ; the workmen are called agate lapidaries and agate borers. The cutting is performed in the large agate mills, on sandstone ; each mill has generally five large sandstones, five feet in diameter and fourteen to fifteen inches in thickness, fastened upon a shaft, ^which causes AGATE. 287 them to revolve vertically, and which are continually moistened by a stream of water. The workman leans with his. body upon a peculiar bench, the seat of which is called the cuirass, and with his feet presses himself against a pole, whence he continually pushes the larger lumps of the agate towards the rnill-stotoe ; this, however, is often made so smooth from the friction, that it is often necessary to make it rough by knocking it with a sharp hammer, according to the kind of work, whether fine or coarse. The stones are either polished on sandstone or on wood, by means of fine clay or powdered chalk ; they are polished sometimes, also, on wooden wheels, covered with lead or tin. Snuff-boxes and other articles of agate, which are hollow, are polished on smaller sandstone wheels, which dimmish in size as the work advances. Agates which require to be bored belong to a particular branch, distinct from the other. The boring is performed by means of a diamond point, and is described by Mr. Mawe. The onyx varieties are mostly employed for cutting cameos, and are prepared there in such a manner that the darker layer is cut for the base, and the lighter for the intended objects. There is in Siberia, at Katherineburgh, an extensive manufactory for grinding and polishing agate and other gems. Many varieties of agate are used for engraving other stones, and also for the Florentine or stone mosaic work. Since agate has always been, and is yet, a favorite. stone, it has been attempted to improve either its color or other "external appearance by artificial or mechanical means ; this is done either by the use of metallic solutions or by boiling in oil of vitriol. The color has often been improved by giving to the stone, before it is polished, several strokes in succession, the small fissures thereby produced displaying an iridescence or some other phenomenon, if held towards 288 A POPULAR TREATISE ON GEMS. the light 5 this operation, liowev.er, may easily be detected by wetting the stone, when the water, entering the fissures, will destroy the effect; it will show itself again when dry. On some agates black and white layers are produced, in order to use or sell them in the place of real onyx ; this operation is performed by the lapidaries, who boil certain varieties in oil of vitriol, which changes the color of some very soon to black, and renders others clear or still paler. Only polished agates are used for this purpose, and the cause appears to lie in the oil absorbed by them during the opera- tion of polishing, on which account agates are by some first boiled in oil before submitting them to the operation of the oil of vitriol. The value of agate, although much reduced in com- parison to former days, a great deal depending upon the purity and perfection of color and peculiar figures, com- mands a pretty good price in the market ; it is particularly the onyx which is yet at high prices, and on that account it is imitated by pasting thin plates of chalcedony, jasper, agate, &c., together, and making them, by their different colors, appear like real onyx ; this deception may, however, be easily detected by putting it into hot water, which disengages the plates one from another ; the onyx is likewise imitated by pastes, and very happily, but may readily be distinguished from them by the hardness and other characters prominent in the real stones. Onyx, which, as already stated, is a .variety of agate, and most frequently of chalcedony, possesses in its in- trinsic characters a- regular alternation of layers, which are more or less thick, and of distinct different colors, usually the grayish white, brown, and black predominating ; while sardonyx indicates one layer or more to be of carne- lian, and this is in higher estimation. It was this stone par- ticularly which the ancients mostly sought after for engrav- AGATE. 289 ing the heads of celebrated persons, their deities, and their idols; the fawn-colored variety, which is neither yellow nor red, was the highest in value. Both onyx and sar- donyx were purchased in Arabia and the Indies, and the harder the stones and finer the grain, the more valuable they were for the purpose of cutting. The title of Oriental onyx was always given to the finest qualities of the stones, regardless of the locality from whence they were brtmght. The Imperial Library at Paris possesses some of the most antique cameos and intaglios of onyx, such as Germani- cus, Marcus Aurelius, Faustina, and Tiberius ; the dread- ful Jupiter is an onyx in two layers ; Venus on a marine- bull, surrounded by cupids, are personifications of the highest perfection in the art. The superb fragment existing in Rome, and representing Antilochus announcing to Achilles the death of Patrocles, is another master-piece ; the cameo has a* black ground, with a white layer above, and the expression of grief on the three faces has secured to this cameo the decided suprem- acy of the ancient over the modern art. The bowl of Capo di Monte, in the Royal Museum of Naples, and the great cameo of Alexander and Olympia, belong to Mr. Bracciano, at Naples. The French Museum contained the great cameo of An- tonius and Faustina, engraved in different colors, but not parallel lines, it is not inferior to any other : the ground, which is of agate of brownish color, is Antonius, and above, in a white layer, is the pleasant figure of Faus- tina, whose drapery and hair ornaments are exceedingly well executed in a lilac color. The sardonyx is also called sarde, and if of a dark sable color, was preferred by the ancients for cutting intaglios. Mars and Venus when surprised by the gods, is executed 13 290 A POPULAR TREATISE ON GEMS. by Valerio Yicentine; it represented nine figures. The Nuptials of Cupid and Psyche contains .five figures. In the inventory of curiosities belonging to the crown of France, made in 1*791, are mentioned two vases of sardonyx, valued at sixty-four thousand francs ; six sets, at one hundred and sixty-seven thousand francs ; two cups at six- teen hundred francs; one decanter at thirteen hundred francs ; one urn at six hundred francs ; but one remarkable sardonyx, of a grayish yellow mixed with brown, on which a Medusa head was engraved, was valued at twelve thou- sand francs. The onicolo or nicolo is another variety of onyx ; it is of brown ground with a band of bluish white ; it is distin- guished from onyx, by the lower layer being always thin- ner than the upper ; it is not so highly valued as either the onyx or sardonyx. The Mineralogical Cabinet at Paris possesses several cameos of this material ; one represents military piety ; also a cameo of Adonis, by Coinus. The stone is probably the cegyptilla, described by Pliny. The real sardonyx is the rarest mineral among that class of stones, on account of the multiplicity of layers, of which there are as many as ten, all, however, from the same sub- stances, but differently colored : such as chalcedony, jasper, agate, white, gray, red, and brown, opaque, translucent, bluish, or yellowish; they are highly prized, particularly those from the Orient. The finest cameo of the real Oriental sardonyx is in the imperial cabinet of Vienna, it is said to come from Diosco- rides ; it was obtained by Rudolph II., the German emperor, for 12,0(70 ducats. In the crown-jewels of France are some unique cameos of sardonyx, such as the triumph of Bacchus and Ariadne, valued at 7000 francs, and eleven other cut stones valued together at 60,000 francs. AGATE. 291 Great collections of antique onyxes, engraved as cameos and intaglios, are in Vienna and Berlin; in the first is to be seen the apotheosis of Augustus, which is ten lines broad and six high, and contains twenty perfect figures ; this was purchased by the Emperor Rudolph at Frankfort-oir-the- Maine, for fifteen thousand ducats. The celebrated cameo in the Vatican Museum, at' Rome, is of agate, and represents Augustus. Italy has always been the great emporium for genuine antique onyxes and cameos, and occasionally we still behold fine specimens of art in the . possession of travellers coming from Europe. A very fine collection of antique cameos and intaglios in precious gems and antique pastes, likewise cameos and intaglios of modern artists, I have seen in this country, in the possession of Thomas G. Clemson, Esq., of Philadelphia. I have in my collection a good onyx of the Emperor Vi- tellius ; a splendid cameo of Bacchus, of two and one fourth inches long and one half inch thick ; one of Antony and Cleopatra ; also a splendid intaglio. In Paris are several celebrated cameos, worthy the notice of travellers going to Europe : the Brunswick Vase was cut from a single stone, and has the form of a cream pot, about Iseven inches high and two and a half broad on its outside, which is of a brown color; there are white and yellow groups of raised figures, representing Ceres and Triptole- mus in search of Proserpine; Agrippina and- her two chil- dren, composed of two layers, brown and white ; the Quar- rel of Minerva with Neptune, which consists of three layers ; Venus on a sea-horse, surrounded with cupids, &c. The Museo Borbonico at Naples contains an onyx meas- uring eleven inches by nine the apotheosis of Ptolemy on one side, and the head of Medusa on the other ; both are splendid specimens of art, and supposed to be the largest in existence. 292 A POPULAR TKEATISE ON GEMS. Two very beautiful flower-vases of black onyx, colored with natural white veins, two large cups of red chalcedony colored, long square links of chalcedony, connected together without joints, and alternating in colors, also a very beau- tiful snuff-box of green jasper, were seen at the London Exhibition, manufactured by Wild & Robinson, in Oberstein. Some modern works of cameo, from the hand of the cele- brated Puckler, are in the collection of Robert Gilmore, Esq., at Baltimore, and in that of W. J. Lane, Esq., of this city, who possesses also a Washington head of black and white onyx, by Isler, which is extremely beautiful; also a s very fine modern cameo in onyx, two inches in length, I saw in Stephen H. Palmer's establishment. CHRYSOPRASE. The ancients by this name designated a stone of a green color, with a yellowish tinge ; but it is not certain whether that which goes by this name, at the present day, is the same. We find, in the fourteenth century, this stone used as ornaments in churches and other places, but it was not known by the above name until 1740, when it was* discov- ered by a Prussian officer in Silesia. Frederick the Second ornamented his palace Sans Souci with this mineral. The common people of Silesia wear the chrysoprase around the neck as a charm against pains. Chrysoprase occurs massive and in plates ; the fracture is even and splintery; it is translucent; lustre, resinous; sometimes dull apple-green, grass-green, olive-green, and whitish-green color ; it scratches white glass distinctly, but is not so hard as true chalcedony; specific gravity, 2'56 ; it is infusible before the blowpipe, but loses its color when heated ; it consists of silex, with a little carbonate of lime, alumina, oxide of iron, and nickel ; its color is imparted by CHRYSOPRASE. 293 the latter substance. This mineral is found in the serpen- tine of Silesia ; also, in Siberia, and in the United States (in New Hampshire). Chrysoprase is used in jewelry and for various ornamental purposes, such as breastpins, rings, bracelets, necklaces, seals, &c. ; and the larger masses are used for snuff-boxes, cane-heads, table-plates, &c. The cutting is pretty difficult, and the greatest care is required for finishing the same with facets, as it is easily fissured ; it is done on tin or lead plates with* emery, keeping the first constantly wet with water ; it is polished on a tin plate with rotten-stone, but the lapidary has always to be cautious not to let it become hot, as it easily splirfters, and grows opaque and gray. The usual cut is the table or cabochon, with facets on the border ; in setting, a foil of green satin is often used for a back, but when pure and of good color, it is mounted djour. Inferior specimens are painted on the back with a mixture of verdigris, white lead, and gum mastic, or with sap-green. The chrysoprase loses its color by wearing; heat and sunlight likewise cause it to fade, and render it dark and cloudy ; but the color may be restored by keeping it in a wet or moist place, such as a cellar, in wet cotton or sponge, or even by dipping it in a solution of nitrate of nickel, which serves likewise to improve the inferior qualities. Very fine imitations in paste may be made by mixing 1000 parts of strass with 5 " of oxide of iron, and 8 " of oxide of nickel. The chrysoprase is subject to a great many faults, such as fissures, either natural or received in cutting ; oily whitish spots, pale gray flaws and stripes, and sometimes small grains of clay of reddish color, intermixed in the interior of the stone ; but when pure, the chrysoprase has always been 294 A POPULAR TREATISE ON GEMS. a great favorite. A good seal or ring stone may be worth from twenty-five to thirty dollars, and smaller specimens from one to five dollars. The apple-green variety is most valued, and a specimen one line long by one half broad, has been sold at from fifty to one hundred and fifty dollars. At Paris, an oval chrysoprase, eight lines long and seven lines, broad, was- sold for three hundred and ten francs. The price generally has decreased of late, on account of the great quantity cut from the mines, which have recently been covered up, in order to raise its value again. At the royal palace of Potsdam, in Prussia, are two tables of chrys- oprase, the plates of which are three feet long, two feet broad, and two inches thick. CHRYSOLITE, PERIDOT, OLIVIN. The name of this stone is of Greek origin, and was well known to the ancients, although it is undecided whether they designated the same mineral by this name that we do at the present time, for they make it in their writings to be either the. topaz or goldstone, or the transparent gold- yellow stone. The chrysolite occurs in prismatic forms, generally a right prism with rectangular bases; also, in angular rounded crystalline grains or massive ; the fracture is conchoidal ; it is trans- parent and translucent; it possesses powerful double-refracting power ; its lustre is vitreous and resinous; the lateral planes of the crystals are some- times striated ; the color is olive-green, turning to yellowish and brownish; it scratches glass indistinctly, and is attacked by topaz ; hardness, 6'5 ; Fig. 10. CHRYSOLITE. 295 specific gravity, 3"33 to 3'44 ; becomes electric by rubbing ; is infusible by itself before the blowpipe, but is dissolved into a transparent pale-green bead with borax; acids do not affect it ; it consists of magnesia, silica, and oxfde of iron. Chrysolite is found particularly in basalt, trap, green- stone, porphyry, and lav% ; sometimes in alluvial deposits and the sands of rivers. The perfectly crystallized chrysolite is brought from Constantinople, but its true locality is unknown ; less dis- tinct crystallizations occur imbedded in Java at Vesuvius and the Isle of Bourbon ; imbedded in obsidian at Reel del Monte,. in Mexico; among sand at Expaillie, in Auvergne, in pale-green transparent crystals. Egypt, Natolia, and Brazil are the principal localities for the prismatic chrysolite; the oh* vin is more frequently found in imbedded crystals, and granular aggregations, in the basalts of the Habichtswald, the Eiffel, the Upper Palatinate, Geysingburg near Altenburg, Kapferistein. in Styria, and in the sienite at Elfaden in Sweden. The brown variety (hyalosiderite) is- found at Sabbach and Iringen on the Kaiserstahl, and hi dolorite, near Rpburg in Baden. Crystals of olivin, several inches in length, occur in green- stone, at Unkle near Bonn, on the Rhine, and it is a fre- quent ingredient of meteoric stones. The word chrysolite is derived from %pv0o$, gold, and /U0of, stone, in allusion to its color. The dark-colored peridots, which take a high polish, are now much worn in Europe ; they lose, however, their gloss very soon, on account of their softening. The ligurite is a species of chrysolite of an apple-green color, is transparent and of uneven fracture; hardness, 5 '3 ; specific gravity, 3*49. Its /4|kimary form is an oblique rhombic prism; the ligurite contains some alumina and lime in addition to the composition of the chrysolite ; it is 296 A POPULAH TREATISE ON GEMS. considered a superior gem to chrysolite, both in color and transparency. It occurs in a talcose rock on the banks of the Stura, in the Apennines of Liguria ; it does not become electrfc by heat or friction. The bot.tlestone of Moravia is likewise a species of chrys olite, of dirty-green and grayisto-green colors, does not occur crystallized, but in flat pieces of about an inch in size ; some specimens which the author collected in his youth, in Moravia, were fair specimens suitable for cutting, their color being dark-green. The chrysolite is cut on a leaden wheel with emery, and is polished on a tin plate with rotten-stone or oil of vitriol. Sometime^ pale stones are finally polished with some olive oil, which, raises the color considerably : this last operation is applied to restore its lustre, after the chrysolite becomes dull 'by wearing. The form is that ojf a rose or table cut ; also in pavilion ; and when set, gold foil is used for its base : the -pale-colored chrysolite looks well with a green-colored copper foil ; dark chrysolites may be rendered clearer by a careful calcination. +'. The chrysolite^ used for rings and pins, but does not stand in high estimation, not possessing either a distin- guished color, strong lustre, or great hardness, and losing its polish by wearing ; on account of its softness, it wears off at the edges. Very good specimens of peridot from Brazil were brought into this country from France, and commanded a good price, a few years ago, viz : from ten to fifteen dollars a carat. Chrysolite was much esteemed by the ancients ; Queen Berenice received a chrysolite as a present from Phile- mon, lieutenant of King Ptolomeus. Cleopatra likewise gave one to Antony. Louis XIII. brought chrysolite into fashion at his court. Among the engravings in chrysolite is one of the Em- IOLITE. 29Y peress Sabine, which is in the cabinet of Crispi, at Ferrara. Among the most extraordinary engravings in chrysolite, is one representing Ptolomeus-Oulet, king of Egypt, and the Nuptials of Cupid. IOLITE. This mineral has for a long time been brought from Spain, but has lately been made known and brought into notice by Cordier, afte'r whom it received the name cor- dierite / it is called likewise steinheilite^ and has several other names, which I will mention, in order that the reader may not be confused when the same mineral is presented as a gem, under different names; the most appropriate name is dichroite, from its property of displaying two colors when held in different directions ; it is also known aspeliom and prismatic quartz. It occurs in regular six and twelve sided prisms ; also, in crystalline grains, massive, and in pebbles ; its fracture is conchoidal and uneven ; it is transparent, exhibiting an indigo-blue color when held in the direction of its axis, or viewed by transmitted light, and appearing brown- ish-yellow when held at right angles ; it possesses some double-refracting power. Sometimes a ray of light, resembling that of the star-sapphire, may be perceived in iolite, particularly when cut; it has a vitreous lustre ; its colors are violet-blue and indigo-blue, sometimes with a tinge Fig. 11, of black and bluish-gray. It scratches glass, and is attacked by topaz ; its streak-powder is white ; hardness, 6'5 ; it ha's a specific gravity of 2*88. By rubbing, it becomes electric, and assumes polarity by heating ; it is difficult to 298 A POPULAR TREATISE ON GEMS. fuse on the edges, and becomes then a grayish-green enamel : borax fuses it into a diaphanous glass ; acids have no effect upon it ; it consists of magnesia, alumina, and silica, with some oxide of iron and water. It is often found under the names of lynx and water sapphire, the first of a pale and the latter of a darkish blue color. It is found in primitive rocks ; also, in blue day, in copper pyrites, in quartz or felspar, and in small de- tached masses ; the localities are at Baldenmays in Bavaria, occasionally in perfect crystallizations, but usually massive ; ' it is associated with magnetic pyrites. The variety from this locality has been called peliom, from its peculiar smoky- blue color, from rrehiog. It occurs in quartz, at Ujordlero- soak, in Greenland ; in granite, at Cape de Gata, in Spain ; at Arehdal, in Norway ; at Orrijervi, in Finland ; at Tuna- berg, in Sweden, &c. Ceylon affords a transparent variety in small rolled masses of an intense blue color. At Had- dam, Connecticut, it is associated with garnet and anthoph- yllite in gneiss. It is occasionally employed as a gem, and when cut exhibits its dichroism, or different colors in different directions. The name iolite is derived from tov, a violet, and /U0o, stone, in allusion to its color. From its property of exhibiting different colors according to the direction in which it was viewed, it has also been named dichroite, from 61$, double, and %poa, color. The hydrous* iolite, from Sweden, of grayish-brown or dark olive-green . color, is a very soft mineral ; hardness, 3'75 ; occurs in red granite, accompanied by a light bluish- gray iolite. If the stone is perfectly pure, it is used for rings and breastpins; is cut on a copper wheel with emery, and polished on a tin plate with rotten-stone, and receives the form of a cabochon, in order to let it display its proper colors, and in a cube form. Its price is not very high ; the PRECIOUS OPAL. 299 jewellers value it as an inferior quality of the sapphire, without paying any regard to its phenomena of light. Good-sized specimens are sold at about eight to ten dollars each ; at Paris, a good iolite, ten lines long and eight and a half broad, was sold for one hundred and sixty francs. When, a couple of years ago, the iolite was discovered by Professor Mather, at Haddam, Connecticut, it promised to be a valuable acquisition to American gems ; but the suppfy was very scant, and its original locality appears to be exhausted. Professor Torrey possesses a fine seal, in the form of a cube, from that locality, which displays its properties to the greatest perfection. A blue quartz is occasionally sold for iolite, but it may easily be distinguished by its colors and hardness. Sapphire is considerably harder than the iolite. OPAL. The precious variety of this mineral was known to the ancients, and received its name on account of the "play of colors which it has. The opal has a great many varieties, which are all considered more or less gems, and find their application in jewelry ; they will therefore be treated separately. But, as general characters, it may now be men- tioned that opal scratches glass but slightly, while it is marked by rock-crystal ; it has a specific gravity of 2'OG.to 2'11 ; it is infusible before the blowpipe, but decrepitates and falls into splinters ; it also dissolves with borax. Opal consists of silica with water, some oxide of iron, and some- times alumina. ' : * PRECIOUS OPAL. This gem derives its name from the Greek word sig nifying the eye, for the ancients believed that this stone 300 A POPULAR TllEATISE ON GEMS. had the. power of strengthening the eye. It was highly esteemed by them, as we learn from l^liny, who thought that the play of color originates from the beautiful colors of the carbuncle, amethyst, and emerald. The phenomenon of the play of colors in the precious opal has not yet been satisfactorily explained. Hatiy attrib- utes it to the fissures of the interior being filled with films of air, agreeably with the law of Newton's colored rings, when two pieces of glass are pressed together. Mohs'con- tradicts this theory upon reasonable grounds, which are, that the phenomenon would present merely a kind; of irides- cence. Brewster concludes that it is owing to fissures and cracks in the interior of the mass, not accidental but of a uniform shape, and which reflect the tints of Kewton's scale ; but it is, in my opinion, sufficiently plausible, that the unequal division of smaller and larger cavities, which are filled with water, produces the prismatic colors, and for the simple reason that" the opal which grows, after a while, dull and opaque, may be restored to its former beauty if put for ti short time in water or oil. Although the precious opal was never found in the East, yet it bears the name of Oriental opal among jewellers: for in former times opals were carried by the Grecian and Turkish merchants from Hungary, their native locality, to the Indies, and brought back by the way of Holland to Europe, as Oriental opals. The precious opal is found, in small irregular gangues, nests of the trachytic por- phyry formation and its conglomerates, in Hungary, par- ticularly in the neighborhood of the village of Czerwin- ccza ; also, in the Faroe Islands, Saxony, and South America. The Hungarian opal is found of various qualities, and is obtained from mines which have been wrought for several centuries ; and, according -to the archives of that part of the country, there were, in the year 1400, more than three PRECIOUS OPAL. 301 hundred workmen engaged at the mines near tlt above village ; whereas there are but thirty at present engaged there, on account of the scarcity of large suitable speci mens. The precious opal is principally used for rings, ear-rings, necklaces, and diadems ; the smaller specimens for mount- ing snuff-boxes, rings, chains, &c. It is ground on a leaden wheel with emery, and is polished with rotten-stone and water on a wooden wheel ; and, in order to increase its lustre, it is lastly rubbed with putty, by means of buckskin, or a woollen rag and red chalk. Its form is generally that of a semicircle, lens, or oval; sometimes of a table, and then also with some facets ; but great care has to be taken that the edges, on account of the softness of the stone, do not wear off. It is also apt to spring in a temperature sud- denly changing. When mounted, it receives a colored foil, or a variegated silk stuff, or a peacock-feather on the back, but it looks best in a black casing. Cracks and fissures may be removed by leaving the pre- cious opal for some time in oil. Very frequently the pre- cious opal is distributed in small particles in the matrix, called mother of opal, which is cut by the jewellers as boxes, and other ornaments 4 and very often, too, this matrix is plunged into oil, and exposed to a moderate heat, whereby the base grows b.lacker, and the true precious opal retains its ray of colors. In order to preserve the surface of the precious opal against wear and tear, it is covered with a thin plate of quartz crystal. The precious opal still stands in very high estimation, and is considered one of the most valuable gems. The size and the beauty displayed by its colors determine its value ; those playing in the red and green colors bear the highest price. Its value has latterly increased on account of the scarcity of the larger specimens. Formerly, a solitary large precious 302 A POPULAR TREATISE ON GEMS. opal, playing in the red color, was sold for two to three hundred ducats; and one playing in both red and green colors, about five lines long, was sold at Paris for two thousand four hundred francs; and lately a single opal, of fine colors, and the size of a dollar, was sold near the locality for three hundred thousand florins ; in this country precious opals are sold by the importers at the rate of four to ten dollars per carat, and single specimens, suitable for pins or rings, from two to twenty dollars. The mother of opal is, however, much cheaper ; one of five lines size is sold for three to five dollars. All experiments for imitating the precious opal have hitherto proved fruitless ; they were made either by pre- paring an enamel and adding several metallic oxides, or by affixing to the back of a clear or common opal or enamel, a polished thin plate of the mother of pearl, which may some- times deceive the ignorant. The precious opal, when large and exhibiting its peculiar play of colors in perfection, is a gem of considerable value; it was used as an ornament among the Greeks and Romans, and was called opalus ; also paederos (Ttaidepd)?) , in allusion to its color and lustre as expressed in the Orphic poem : " Ipeprov repeva xpoa naidbs, having the delicate com- plexion of a lovely youth." The most magnificent Hunga- rian opal in the London Exhibition, called "the mountain of light" a very appropriate name weighed 526 carats, and was estimated at 4000 pounds sterling. From Honduras, at Gracias a Dios, large quantities of opals have been imported into this city for the last ten years, at first by the late Mr. De la Raye, and latterly by Mr. Aaron C. Burr ; and many large and beautifully cut speci- mens are in the possession of Mr. B. Palmer, of this city; they are by no means inferior to the Hungarian opal. A very large opal, cut and polished by himself, which he PRECIOUS OPAL. 303 values at four thousand dollars, is one and three quarters inches long by one and a quarter inches wide ; another, one and a quarter inches long by one inch wide, he prizes at. seven hundred and fifty dollars; and a third, one and one eighth inches long by one inch wide, he values at four hundred and fifty dollars. The ancients held the opal in great estimation, and the anecdote of the Roman senator, Nonius, is well known that he preferred exile to parting with a magnificent opal which Marc Antony coveted. In the French crown-jewels are two very large and beautiful opals. One is set in the centre of the Order of the Golden Fleece, and the other forms the clasp of the imperial cloak. They were purchased for 75,000 francs. The Empress Josephine possessed the unique oppl which was called " The Great Fire of Troy," on account of the great fire sparkles. The Vienna Cabinet possesses a very large opal, but unfortunately it is cracked. Count Walewski, who is a great amateur of gems, possesses a very beautiful opal, which is oval, the size of a franc-piece, and is said to be extraordinarily brilliant, The Imperial Mineralogical Cabinet at Vienna, contains the most celebrated specimens of precious opal ; one, par- ticularly, may be mentioned here: it is four and three quarter inches long, two and a half inches thick, and weighs seventeen ounces. It was discovered about' 1770, at the above locality, and transported to Vienna. It displays the most magnificent colors ; is perfectly pure, and not accom- panied by any. matrix. Half a million of florins were offered for it by a jeweller of Amsterdam, and refused on account of its uniqueness ; and the Viennese have not yet dared to put even any approximate value upon it. 304 A POPULAR TREATISE ON GEMS. FIRE OPAL. This mineral was first brought into notice by Baron Humboldt, who found it in Mexico. It occurs massive ; has a conchoidal fracture ; is trans- parent ; of strong vitreous lustre ; color, hyacinth-red, run- ning into honey, wine-yellow, showing carmine-red and greenish reflections ; sometimes containing dendritic draw- ings. Its specific gravity is 2 '02 ; loses one and a half per cent, by calcination, and leaves pale flesh-red fragments. It is found in the trachytic porphyry, in Mexico, and in the amygdaloid of the Faroe Islands. As the fire opal is very little known, it has not yet been employed in jewelry, but bids fair to find applica- tions. It is ground on a leaden wheel with emery, and polished with rotten-stone on a wooden wheel. The forms of cabochon, table, or pavilion, might suit very well as ring- stones. The cabinet of the university of Bonn possesses a very large and fine fire opal, of the size of the fist. The largest specimen I have seen is in the royal mineral ogical cabinet at Berlin, which was deposited by Baron Humboldt on his return from South America, and which, if I recollect it well enough from the year 1827, must be at least six inches long and four inches thick. This is the largest specimen he ever found. A collection of six shades of fire opal, with six more varieties of the other opals, was presented to me in the year 1828, when in Berlin, by the Counsellor Berge- man, who received at that time a considerable quantity of polished specimens from the Faroe Islands, but all of small size. A splendid collection of fire opals was brought from Guatemala some years ago to this country. It is also called girasol, from its bright hyacinth-red tints. HYDROPHANE. V , 305 CO3CMOX OPAL. This mineral occurs massive and in rolled pieo^; also as stalactites; has a cOnchoidal fracture; is transient and semi-transparent ; has a strong vitreous and resinous lustre ; its colors are. milky, yellow, reddish, greenish- white, honey- yellow, wine-yellow, flesh, brick-red, and olive-green ; some- times dendritic (moss opal). Its specific gravity is 1 '9 to 2*1. The wax or pitch opal is subordinate to this variety. It is found in the same rocks as the precious opal, in Hun- gary ; in the hematite rocks of Saxony ; in the serpentine of Silesia; in cavities of trap and the amygdaloid rocks of Iceland ; 'Faroe Islands ; and in the United States (Penn- sylvania and Connecticut). It is used for rings, pins, and cane-heads ; but is, on the whole, not a favorite among jewellers, ar, which is found in volcanic rocks, occurs crystallized in the Vesuvian lavas, and is of a white color. Murchisonite is a yellowish-gray variety of felspar, from Dawlish and Arran. Leclite^ or the hettefliata of the Swedes, has a peculiar waxy lustre and a deep flesh-red color, and is found at Gryphyttan, in Sweden, Conazeranite is a grayish-black or blackish-blue variety, from the steep defiles of Salleix, in the Pyrenees ; it occurs imbedded in limestone. Variolite is a dark-green variety of felspar, containing lighter globular particles ; originally found in Drac river, in France, but of late also in Piedmont, Switzerland, and Scotland ; in the Alps large blocks of several thousand pounds are found. This stone, when polished, takes a high gloss, equal to the most precious gems. Its name is derived from the peculiar spots flashing around the stone. The name adularia is derived from Adula, the ancient name of St. Gothard, where the prettiest specimens were first discovered. A very curious variety has been found in Siberia, of a yellowish color, but with innumerable gold spots dis- seminated throughout' the whole surface of the mineral; these reflections of light appear to be owing to very small fissures or cracks, or to a confusion of its lamellar system. The prettiest specimens, which are invariably cut in cabo- chon, look much like a reflection of a star, diverging from the centre ; they are very rare, however. This variety of moon-stone has often been confounded with the Oriental avanturine, but on examination may at once be detected. COMMON FELSPJte. 315 The Ceylon variety ought only to be called Oriental moon- stone, from the peculiarity that it is more uniform, not striated like that from St. Gothard, and having also a brighter lustre; its chatoyant qualities are therefore more prominent. Sun-stone contains minute scales of mica, and reflects a pinchbeck-brown tint. COMMON FELSPAE. This felspar occurs in crystals, massive, and disseminated ; its fracture is uneven and splintery ; is translucent ; has a pearly and vitreous lustre ; its colors are white, gray, red, yellow, and green, in their various shades, sometimes with a variegated bluish, greenish, or reddish play of colors ; its texture is compact, or minutely foliated. The amazon-stone, or green felspar, is from Siberia ; like- wise splendid grass-green felspar has been found in the Uni- ted States, at Southbridge and Hingham, Massachusetts, and Cow Bay, New York; of apple-green color, at Topsham, and near Baltimore, Maryland. Also, the American glassy or vitreous felspar, found in Delaware, which ought prop- erly to be quoted as a distinct species, is arranged with this variety. Felspar is widely diffused all over the globe, and with a few exceptions is more common than any other mineral ; it forms a constituent part of most primitive rocks, such as gneiss, granite, &c. ; is the principal ingredient of the sienites, porphyry, and, in fact, with a small percentage of other minerals, forms whole mountain ranges and chains in various parts of the globe : such we see in Siberia, the north and west of Scotland, &c., all of which are surrounded by felspar. Immense beds exist in the United States : around Wilmington, in the State of Delaware, is an inexhaustible deposit of exquisite and perfectly pure felspar; and ID 316 A POPU1*E TREATISE ON GEMS. Connecticut and on the North River we see beds of the foliated felspar extending for miles. Sweden, Norway, and Greenland are likewise great depositories of the common felspar. The amazon-stone is used in jewelry for rings, pins, seals, snuff-boxes, &c. It is principally cut at Ekaterinen- burg, Siberia, where it is ground on a leaden wheel with emery, and polished with* rotten-stone on a wooden wheel; its form is that of cabochon, and sometimes that of the mixed pavilion-cut, when the table is to be cut pretty large, and arched, in order to display more distinctly its peculiar colors. Common felspar is of no great value, and . only the ama- zon-stone is used in jewelry, which commands a good price. Cut specimens, suitable for ear-rings or brooches, are worth from three to five dollars. A very fine specimen of the amazon-stone, in its rough state, may be seen in the New York Lyceum of Natural History. The imperial cabinet of St; Petersburg possesses two vases of this stone, which are nine inches high and five and one half inches in diameter. Although our vitreous felspar has not yet been brought into use for the purposes of jewelry and other ornaments, yet it bids fair to con- tribute, at one day, much to the national wealth of this country, for it is the best material for porcelain, china, and earthen-ware. Already have many cargoes of this beautiful mineral been shipped to France and England (six hundred tons of the Connecticut, Middletown, felspar were, accord- ing to Professor Shephard, last year shipped to Liverpool, and one hundred tons to the Jersey porcelain manufactory), where the manufacturer appears to appreciate better the purity of ingredients for the purposes just mentioned. In- stead of receiving, as hitherto, the manufactured goods from abroad, made of our own raw material, it is earnestly LABRADOR. 317 to be hoped that w will shortly acquire skill, and exert sufficient industry to compete with loreign manufacturers in the art of making porcelain, with the superior material which nature has so abundantly lavished on this continent. I possess a splendid slab of the vitreous felspar, of one square foot, free from any admixture, and imposing in appearance. LABRADOR. This mineral was heretofore considered as a variety of felspar; but it has latterly been separated from it, and ought, therefore, no more to be called labrador felspar, the name by which it is known in all mineralogical works. Labrador was first discovered by the Moravian mission- aries on the island of St. Paul, on the coast of Labrador; and, according to others, by Bishop Launitz, in 1775, when it was first brought to Europe. Labrador occurs in crystalline masses, massive, and in boulders; it is of an uneven and conchoidal fracture ; its lustre is vitreous, and in one direction pearly; it is translucent; its colors are gray, with its various shades, such as blackish or whitish- gray, with spots of an opalescent or iridescent vivid play of colors, consisting of blue, red, green, brown, yellow, or orange, according to the direction in which light is falling upon the specimen ; sometimes several of these colors arje perceptible at the same instant, but more commonly they appear in succession as the mineral is turned towards the light. These colors are said to originate in fissures which intersect the texture of the mineral, as they are only per- ceptible from that side where they fall together with the foliated structure, and not like the opal, whose mass is sup- plied with fissures running in all directions. Labrador scratches white glass, is? scratched by rock- crystal, and is somewhat less hard than felspar ; its specific 318 A POPULAB TREATISE ON GEMS. gravity is 2'7l to 2'75 ; before the blowpipe it fuses with difficulty, and is said to lose its play of colors ; it consists of silex, alumina, lime, soda, with some oxide of iron and water. Labrador is found as a rock and boulder, in St. Petersburg, Norway, Bohemia, Saxony, Sweden, St. Paul's Island on the coast of Labrador, and in the United States, in Essex county (New Jersey), at the mouth of the North River, and near Lake Champlain, New York, where, according to the description given me by Archibald Mc- Intyre, Esq., its splendid colors are seen on both sides of the water, but a few yards apart, and the effect of the rays of the morning sun falling upon the rock and water at the same time, is said to equal that of the prismatic spectrum thrown into a dark room. Labrador is used for rings, pins, buttons, snuff-boxes, letter-holders, cane-heads, and other ornaments, such as vases and larger articles; but care has to be taken in grinding, that the direction where the *play of colors is visible is kept straight, and that it is cut in cabochon. The price of labrador is not very high, but soon after its discovery, a Doctor Anderson, having described the min- eral as displaying all the variegated tints of color that are to be seen in the plumage of the peacock, pigeon, or most delicate humming-bird, and specimens having been carried to England, so great was the avidity to possess it, that small pieces were sold for twenty pounds sterling. The present price of good specimens is from two to ten dollars ; and a few years ago I purchased some letter-holders, which are beautiful specimens, for which I paid four dollars each. The largest specimens of labrador are in the col- lection of the Minerajogical Society, and in the museum of the Academy of Sciences at St. Petersburgh, which were found on the shore of the Pulkouka j one of them weighs (en thousand pounds. I have in my possession a rough LABEADOE. 319 specimen of the labrador of this State, merely rubbed off on the surface, and its colors, I venture to say, equal, if they do not indeed excel, in every respect, those of the specimens from St. Paul's Island ; and I anticipate the day when the citizens of New York will take as much pride in possessing labrador table and mantel slabs, as they now do in employing the Italian and Irish marble for these pur- poses ; for the resources appear to be inexhaustible in the rocky county of Essex. We do not see many specimens brought from the coast of Labrador, and I was informed by Mr. Audubon, on his return from that quarter, that he could not find any specimens. Mr. Henderson, of Jersey City, who presented me the above-mentioned rough speci- men, had likewise splendid small polished specimens in breastpins, displaying all the properties in their full beauty. The same gentleman, who travelled last summer in com- pany with several scientific State geologists, mentions that they picked up beautiful specimens at the height of five thousand seven hundred feet above the level of the sea. In the collection of Columbia College is a fine specimen of labrador, brought from Gaspe, Lower Canada, by the Hon. Mrs. Percival. In 1799, it was announced" that in Russia* a labrador spar was discovered, where a perfect drawing and image of Louis XVI. could be distinctly traced, his head surrounded by a colored crown of pomegranate, with a rainbow border, and a silvery plume of azure color ; it was what may be called a lusus naturae. Count de Robassome, .formerly in the Russian service, was the possessor of this singular stone, and he demanded for the same, the sum of 250,000 francs. There were some magnificent specimens, tables, and other ornaments, in the London Exhibition. 320 A POPULAR TREATISE ON GEMS.* In the New York Exhibition, were likewise fine speci mens exhibited from Labrador and the New York locality. HYPERSTHENE. This mineral was formerly annexed to hornblende, but has latterly been separated ; its name is derived from the Greek, and means of superior strength, in reference to the great hardness and specific gravity which it possesses. Hypersthene is found in crystalline masses ; it has an un- even fracture ; it is opaque, and its colors are dark-brown, red, and greenish or grayish black ; the cleavage is parallel to the sides, and shorter diagonals of a rhombic prism ; its lustre is metallic, and when viewed in one certain direction, copper-red, light-brown, or gold-yellow, and in others it has a greenish play of colors. It scratches glass, has a darkish-green streak-powder, and has a specific gravity of 3'38 ; it is easily fusible before the blowpipe on charcoal into a grayish-dark bead ; acids have no effect upon it ; it consists of magnesia, silex, alumina, and lime, with some water. It is found forming a constituent of the labrador rock, on the coast of Labrador, Greenland, and in the United States, on Brandywine creek in Pennsylvania, and in Essex county, New Jersey; fine specimens have been found in Hingham, Massachusetts. The French jewellers have lately begun to introduce this mineral for rings, pins, and other ornaments, on account of its high polish and beautiful color. The best-colored pieces are cut out of the mass, and ground on a lead wheel with emery in cabochon, and polished with rotten-stone. Beauty of color and other qualifications determine the price of this stone ; at Paris a hypersthene, in cabochon cut, eight to ten lines long and six lines broad, was sold for one hundred and twenty francs. IDOCEASE. 321 The mineral is, however, pretty rare, and has not yet been fully introduced. EDOCEASE. This mineral occurs mostly crystallized, in the form of a four-sided prism, terminated by four-sided pyramids ; also, massive ; its cleavage is parallel to all the planes of the prism ; it is transparent and opaque ; possesses strong double refraction of light ; its lustre is between vitreous and resinous ; its cross fracture conchoidal ; the crystals are all striated in length ; its colors are yellowish or brownish green, orange-yellow, sometimes blue and black. It scratches white glass and felspar, but is scratched by topaz. Its streak-powder is white, and it has a specific gravity of 3 '8 to 3*4. Before the blowpipe, it is fusible into a brownish glass. It consists of lime, alumina, silex, with some oxide of iron and manganese. Idocrase is found in different geological positions in primitive and volcanic rocks, in the cavities of the serpen- tine in the Alps, in Piedmont, Mount Soinma, Vesuvius, Etna ; also, Norway, Sweden, Spam ; in the United States, at Worcester, Massachusetts; Salisbury, Connecticut ; Cum- berland, Rhode Island. Idocrase, of pure green and brown colors, and transpar- ent, is used for rings and pins, and at Naples and Turin, it is principally cut for jewelry on a leaden wheel, and is polished on wood with pumice-stone. The forms it receives are the brilliant, table, and pavilion, and if perfectly pure, is mounted d jour ; otherwise with a suitable foil. The price of idocrase is not very high, as it is but little known among jewellers. Chrysolite and the green garnet are often substituted for idocrase ; but the first has a greater specific gravity and is HO 322 A POPULAR TEEATISE ON GEMS. of a more vivid color ; the latter is harder, and likewise of greater specific gravity. The Italian ido erase, which is cut at Naples, is mostly called the Italian chrysolite. HAUYNE. The name of this mineral was given in honor of the celebrated French mineralogist, the Abbe Hatiy. It occurs in dodecahedral crystals, with brilliant faces ; also, in grains and massive ; it has a conchoidal fracture ; is transparent and translucent ; possesses a strong vitreous lustre ; its structure is imperfectly foliated. Its colors are indigo, sky, and smalt blue ; also, white, green, gray, and black. It scratches white glass and is scratched by quartz; white streak-powder; specific gravity is 2*47. Before the blow- pipe it loses its color and fuses into a porous glass, and with borax into a diaphanous glass, which turns yellow on cool- ing; it forms a jelly with acids. , It consists of lime, alumina, silex, protoxide of iron, sulphuric acid, and soda or potash. It is found in slacked basalt, and ejections of Mount Ve- suvius ; on Bodenmaise, on the Laach Lake, in Italy, and on the island of Tiree, Scotland. Hatiyne is not much known yet, but has lately been used for rings, ear-rings, brooches, &c. ; it is cut like ido- crase, but the price will always be high on account of its scarcity. LAPIS LAZULI. The name of this mineral is derived from the Persian language, and means blue color, or, with the Latin prefix, blue stone. The ancients were well acquainted with it, and have employed it as a substitute for other gems. The LAPIS LAZULI. .323 Greeks and Romans are said to have called it by the name of sapphire, denominating that with specks of iron pyrites the sapphirus regilus / Pliny called it the cyanus. It was formerly used as a strengthening medicine. Lapis lazuli very seldom occurs crystallized ; its regu- lar form is the oblique four-sided prism ; it mostly occurs compact, and in grains and specks, with an uneven and conchoidal fracture; it is translucent on the edges; its lustre is nearly vitreous and shining ; structure foliated ; its color is fine azure-blue, with different shades, often inter- spersed with spots and veins of pyrites. It scratches glass, but is attacked by quartz and by the file ; its specific gravity is 2'3 ; before the blowpipe and on charcoal it with difficulty runs into a white glass, but with borax it fuses with effervescence into a limpid glass. It consists of lime, magnesia, alumina, and silex, with soda, protoxide of iron, and sulphuric acid. It is generally called in trade, the Armenian-stone. It is found in gangues of the older formations, and in Bucharia ; it exists in granite rocks, and is disseminated in all veins of thin capacity ; on the Baikal Lake it is found in solid pieces; also, in Siberia, Thibet, China, Chili, and Great Bucharia. Lapis lazuli is much used for jewelry, such as rings, pins, crosses, ear-rings, &c. The best pieces are generally cut out from larger lumps by means of copper saws and emery, then ground with emery on a lead wheel, and polished with rotten-stone on a tin wheel. The rocks which yield lapis lazuli, where it is contained in specks, are likewise cut for ornamental purposes, such as snuff- boxes, vases, candlesticks r cups, columns, cane-heads, &c. ; also, for architectural ornaments and stone mosaic; the larger specimens, having specks regularly disseminated on a white ground of the rock, are those selected for cutting. 324 A POPULAR TREATISE ON GEMS. The most important use of this mineral is that of furnish- ing the celebrated and beautiful pigment called ultramarine- blue, used by painters in oil, and said never to fade. The lapis lazuli takes a very high polish, but becomes dull again after being used for some time. It is sometimes imitated by lazulite' (azure-stone), or blue carbonate of copper, which, however, is not near so hard, and -effervesces- on testing with nitric acid. Those specimens having iron pyrites inclosed are difficult to polish well, on account of the un- equal hardness of the two minerals. Lapis lazuli has latterly been discovered in California, but the color of the mineral from this locality is very in- different, and its price is therefore much inferior to that from Persia. In Paris, the price is estimated at 300 francs per kilogramme. There are many engravings in lapis lazuli, such, for instance, as the Emblem of Peace a figure with a torch in one hand and a cornucopia in the other, and appearing to embrace military trophies, placed before her. The Chevalier d'Azara, Spanish minister in France, pos- sessed while there a very beautiful cameo of lapis lazuli, representing the head of Medusa, but without serpents. Maffei speaks of a Venus being carried by a she goat whipped by Love. The French crown-jewels contained some fine and gigan- tic specimens of lapis lazuli : one in the form of a boat of large dimensions, valued at 200,000 francs ; a sabre-handle given to Louis XVI., by Tippoo-Saib, valued at 6000 francs ; a large vase, valued at 2600 francs. In 1855, at the Paris Exhibition, were numerous objects and carvings, exhibited by Rudolphi, which fairly compared with the antique relics of this species, both in material and in taste of execution. A marine shell carved from lapis lazuli was beautifully mounted by Morrel, and another chefcPoeuvre, in lapis lazuli, LAPIS LAZULI. 325 by Duponchel. A small round table of mosaic and lapis lazuli, which was a beautiful work by Jarry. A magnificent bagnivola of lapis lazuli, of very large size, and extremely pure and rich in color, was exhibited by Mr. Jones, in the London Exhibition, in 1851. Lapis lazuli has been well imitated of late, and, but for the touch, with much difficulty to be distinguished from the genuine, it is manufactured from bone-ashes and oxide of cobalt. The value of lapis lazuli, although depending upon its purity, intensity of color, and size, has nevertheless much diminished when compared with its former prices. . The Chinese, who have for a long time employed lapis lazuli in their porcelain painting, call the pure and sky- blue stone zuisang, and the dark-blue, with disseminated iron pyrites, the tchingtchang, preferring the latter to the former ; they work the same for many ornaments, such as vases, snuff-boxes, buttons, and cups. In the palace which Catharine II. built for her favorite, Orlof, at St. Petersburg, there are some apartments entirely lined with lapis lazuli, which forms a most magnificent deco- ration. I have several slabs, three inches long, and of fine azure-blue color, in my possession. The production of ultramarine has been known since 1502, and was already employed, under the name of azurum ul- tramarinwtn, by Camillas Leonarus. The process of preparing ultramarine was known as early as the fifteenth century. The color is now mostly prepared at Rome, in the following manner : those pieces which are free from pyrites specks, are first calcined and pulverized ; the powder is then formed into a mass with a resinous cement (pastello), and fused at a strong heat ; this is then worked with the hands in soft water, whereby the finest coloring particles are disengaged in the water, 326 A POPULAR TBEATISE ON GEMS. which will soon be impregnated with the blue color ; a fresh portion of water is then taken, and the same operation is continued until the remains are colorless. The ultramarine, after a short time, settles to the bottom of the vessels, and is carefully separated and dried. If the lapis lazuli be of the best quality, the product will be from two to three per cent. That color which remains yet in the mass is of an inferior quality, and is called the ultramarine ashes ; it is of a paler and more reddish color. Good ultramarine has a silky touch, and its specific gravity is 2*36. It does not lose its color if exposed to heat, but is soon discolored by acids, and forms a jelly. In order to distinguish the pure ultramarine from numerous spurious and adulterating coloring materials, such as indigo, Prus- sian-blue, mineral-blue, . The Potomac marble, which is properly called a breccia, being composed of rounded and angular frag- ments from the size of a pea to that of an ostrich's egg. Its colors are red, white, gray, and blackish-brown, inter- mixed ; it takes a very fine polish, and forms a most beau- tiful ornamental stone. It comes from the banks of the 384 A POPULAR TREATISE ON GEMS. Potomac, in Maryland. As specimens of this, we would refer to the .columns in the House of Representatives at Washington, which are twenty feet high, and two feet in diameter. c. The Yerd- Antique, of New Haven, Connecticut. This marble is intermixed with serpentine veins, and makes a most beautiful appearance. There are inexhaustible quar- ries of it at New Haven and Milford ; it bids fair to rival every other ornamental stone in the world. Four chimney- pieces of this mineral were purchased for the Capitol at Washington; and I lately examined a splendid centre table, wholly cut from this marble, that was exhibited at the tenth annual fair of the American Institute. It is to be hoped that some company may undertake to introduce this marble more extensively into notice, for it does not yet appear to be sufficiently known among our wealthy citi- zens: the enterprise would be well rewarded. Large slabs may be seen at the New York Lyceum of Natural History, and in the cabinet of Yale College, New Haven. I possess a very fine, large slab, polished. Portsmouth, Vermont, like- wise furnishes splendid verd-antique, specimens of which may be seen at the American Institute, in New York. d. Berkshire county, in Massachusetts, may justly be called the marble pillar of the United States ; and, as Pro- fessor Hitchcock remarks, the inhabitants of that county cannot but regard their inexhaustible deposits of marble as a rich treasure to themselves, and an invaluable legacy to their posterity. The towns, West Stockbridge, Lanes- borough, New Ashford, Sheffield, New Marlborough, and Adams, in that county, keep thousands of hands constantly working in their quarries. In 1827, two thousand seven hundred tons of marble were exported from that town ; and in 1828, a block of from fifty to sixty feet square, and eight thick, was raised by one charge of gunpowder. 385 e. White, fine, granular marble, bearing the closest re- semblahce to the celebrated Carrara marble, is' obtained from Smithfield, Rhode Island ; Stoneham, Massachusetts, and near Hastings, on the Hudson river. Shell Marble. This mineral is a secondary marble, and is called also conchitic marble, on account of its containing petrified shells, which, when polished, conimunicate to their matrix, the marble, a most beautifully variegated appearance. a. The Lumachella marble is a kind which is very scarce; it has a gray or brown ground, interspersed with shells of a circular form and golden color, and when held towards the reflection of light, displays red, blue, and green tints, like those of the precious opal or iridescent labrador.' It is sometimes seen in the form of pins and other jewelry, but stands,, on account of its scarcity, very high in price ; the only locality is in Carinthia ; . one formerly in Devon- shire, England, being exhausted. Some splendid specimens from Carinthia, are in the collection of Baron de Lederer, Austrian consul for this city ; and a very fine specimen of the lumachella, at the Boston Society of Natural History, was marked with the locality of Neufchatel. b. Panno di morto, or funeral pall, is a deep black marble, with white shells, like snails; it is only seen at Rome, and is very scarce. c. Bristol marble, from England, is a black marble, inter- spersed with white shells. d. Italian shell marbles from Florence, Lucca, and Pisa, are red, containing white shells (ammonites). e. French shell marbles are very numerous ; those from Narbonne are black with white belemnites ; that from Caen is a brown marble with madreporites j and those from 17 386 A POPULAR .TREATISE ON GEMS. Languedoc are of a fiery red color, mixed with white and gray univalve shells ; of this Napoleon's eight columns for his triumphal arch in the CarouselJ at Paris, were cut. f. The United States "have a great many shell-marble quarries ; but they are all black and gray. Those of Tren- ton Falls, Little Falls ; near Seneca lake ; Northumber- land county, Pennsylvania; Bernardston, Massachusetts, and Hudson, New York, contain either trilobitea or encri- nites ; some take a very fine polish. PISOLITE AND OOLITE. These minerals are likewise composed of carbonate of lime; they occur massive, and in distinct concretional layers, either in the form of peas or other round grains or pebbles, and are of white, yellowish-white, brownish, or reddish color ; when cut and polished, they make a fine ornamental stone, and present a very effective appearance. The former is found in alluvial deposits of the hot water mineral springs of Carlsbad, in Bohemia, and the baths of St. Philip, in Tuscany ; the latter forms large beds in Eng- land and France. The city of Bath, in England, is mostly built of this limestone. ROCK OF GIBRALTAR. This is likewise a carbonate of lime ; occurs massive, mostly striped ; is yellowish-white, yellow, and brownish ; is only found in that rock from whence it takes its name, and has been heretofore a great favorite for jewelry and other ornaments. At this day we see in shops and private houses, pins, brooches, ear-rings, seals, cane-heads, snuff- boxes, letter-holders, vases, urns, candelabras, obelisks, &c. 3 formed of it. It takes a high polish. APATITE. 387 APATITE. This mineral was named by Werner, on account of its color being so deceptive (anaraa), to deceive), as it resembles the color of some -other precious stones ; it occurs in six- sided prisms, massive and globular ; has a conchoidal frac- ture ; a vitreous lustre ; color usually sea-green, bluish-green, or violet-blue, sometimes white, occasionally yellow, gray, and red ; is transparent and opaque ; it resembles the beryl and emerald, but is distinguishable by color and hardness ; hardness, 4'5 to 5 ; specific gravity, 3 to 3'235. A bluish opalescence is observed in the direction of the vertical axis in some specimens, especially in the white variety; fracture conchoidal and uneven ; brittle. Some varieties are phos- phorescent when heated, others become electric by friction. It is infusible alone before the blowpipe, except at the edges; dissolves slowly in nitric acid, and without effer- vescence. Apatite usually occurs in primitive rocks ; is often found in veins of primitive limestone traversing granite, it also occurs in serpentine and in ancient volcanic rocks. It contains about ninety per cent, subsesquiphosphate of lime, and the rest is chloride and fluoride of calcium. On account of its phosphoric acid, the compact varieties of apatite have become an important article of trade for agri- cultural purposes. The principal localities are in Saxony, at Ehrenfriders- dorff, in the Hartz mountains, where the author collected, in his youthful years, some magnificent crystals; also in Bohemia, at Schlackenwald ; in Cumberland arid Devon- shire, England; at t. Gothard, in Switzerland; and a greenish-blue variety, called moroxite, is found in Norway, at Arendal. Asparagus stone, which is of a yellow color and trans- 388 A POPULAR TREATISE ON GEMS. lucent, is found at Estremadura, in Spain, of which many fine specimens may be seen at the Academy of Natural Sciences of Philadelphia, in Maclure's collection ; also in Zillerthal, Tyrol, where it is imbedded in talc. The phos- phorite, or massive varieties, from Spain and Bohemia, has been found in large beds. In the United States it occurs in a vein of limestone intersecting the granite at Gouver- neur, St. Lawrence county, New York, and crystals of ten to twelve inches long and one and a half to two inches in diameter, of fine sea-green color, were formerly found in abundance. Yale College has some fine specimens of this crystallized variety, from Baron Lederer's cabinet. Professor Shep- herd, Mr. Francis Algar, and Dr. Charles T. Jackson, in Boston, possess many fine and large crystals. Mr. Kranz, in Bonn, was fortunate to procure, through his collector, some gigantic crystals of this beautiful mineral. There are some other localities of the crystallized variety in the United States, such as Amity, New York, where it occurs of a green color in white limestone, presenting the primary form, and accompanied with pyroxene and scapolite. Crys- tallized and massive specimens of a bluish-green color occur at Boston, Massachusetts, associated with sphene and petalite. Reddish-brown crystals,- of one inch in length, have been obtained from a granite vein in Greenfield, New York. The massive variety of phosphate of lime from Crown Point, New York, has furnished several thousand tons for export to England as a fertilizing agent, and the concretional variety of phosphate of lime from Dover and Franklin, in New Jersey, has likewise yielded considerable quantities for a manure. These two latter varieties have been treated with sulphuric acid (oil oT vitriol), in order to obtain a superphosphate of lime, which is now considered the most useful vehicle to enrich the soil, and to produce MICA. 389 the most prolific crops. Liebig and Johnstone, the two great agricultural chemists, have demonstrated beyond any controversy that .the resuscitation of worn-out soils depends materially upon the addition of phosphate of lime ; and hence the application of bone-dust, which is a phosphate of lime, and guano, which contains the latter ingredient with the ammoniacal salts in combination, of which at the present day 100,000 tons are annually consumed by the farmer, along with the artificially prepared superphosphate of lime, are well known, but do not belong here. LEPIDOLITE. This mineral derives its name from the Greek language, from its scaly structure ; it occurs massive, presenting an aggregate of minute, shining, flexible scales or hexagonal plates ; it has a splintery fracture ; a glistening and pearly lustre; is translucent on the edges; its colors are lilac, rose-red, pearl-gray, greenish-yellow, and blue ; it is scratched by glass, and yields to the knife ; has a specific gravity of 2'81 ; is fusible with ease into a transparent globule. It is found in granite and primitive lime, in Monrovia, France, island of Elba, Corsica, Sweden, and in the United States, in Maine, New Hampshire, Vermont, and Massachusetts. It is cut in Europe for various orna- ments, such as plates, vases, snuif-boxes, &c., and will, 'I trust, at some future day, be more extensively used in jewelry ; for there are some variegated specimens of a peach-blossom color, and very fine granular structure, which are extremely beautiful. MICA. This mineral occurs crystallized, in six-sided tables and oblique rhombic prisms, and massive ; also, disseminated ; 390 A POPULAR TREATISE ON GEMS. it has a perfectly foliated structure ; a glittering and metallic lustre ; is transparent and translucent ; very fusi- ble and elastic ; its colors are white, green, black, brown, peach-red, yellowish, and bluish ;. it has a specific gravity of 2'7. It is found in primitive rocks, and forms an ingre- dient in granite, gneiss, mica slate, and other rocks, where it more or less predominates ; its localities are, therefore, universal, but in Siberia it forms large beds, and is quarried for special purposes, such as a substitute for glass windows ; and although the United States afford ample localities of it, yet a few years ago quantities were imported here for the doors of Nott's stoves. The plumose mica is a beautiful variety, and derives its name from its resemblance to a quill or plume, the lamellar or fine delicate crystals diverging in such a manner as to present this appearance. It is of a pearl-gray color. It is found in the United States, at Williamsbury, Mass., Hart- ford, Conn.,, and many other places. The green mica is of a beautiful grass-green color, and is found in Brunswick, Maine. The rose-red mica is a very beautiful mineral, and is found in numerous places, in this country ; principally at Goshen, Chesterfield, Mass.; Acworth, N. H. ; Bellows Falls, Vt., &c. Mica may, when of good colors, be used for jewelry and other ornaments, as well as the lepidolite. PYRITES. This mineral is called sulphuret of iron, iron pyrites, and markasite. It occurs crystallized in many forms ; such as the cube, octahedron, and dodecahedron ; also massive, disseminated, capillary, and cellular; it has a conchoidal fracture ; a brilliant metallic lustre ; its colors are bronze, yellow, brass-yellow, and steel-gray. This mineral takes a very high polish, and from its fine lustre looks extremely PORPHYRY. 391 well when cut in the form of a brilliant or rose. It was formerly much -used in jewelry for ear-rings, rings, pins, and necklaces. It was, in former times, considered a great preservative of health. It is now but seldom seen, except in mineralogical cabinets. ROSE MANGANESE. This mineral is called in mineralogical works the silicious oxide of manganese, and also the carbonate of manganese. It occurs massive; has a foliated structure; a conchoidal fracture ; a shining lustre ; it scratches glass ; its colors are rose-red, reddish, and yellowish. It is found in Siberia, Sweden, Hungary, England ; and in the United States, at Middlebury, Vt., and at Cumming- ton and Plainfield, Mass., where, according to Professor Hitchcock, the silicious oxide, or according to Dr. Thomp- son, the bisilicate of manganese is found in great abundance. Since it takes a very high polish, and is much wrought at Ekaterinenburg, in Siberia, into many ornaments, it is con- fidently to be hoped that it may also find its amateurs in this country, as it is very easy to cut and polish, and the material is so plenty. PORPHYRY. This mineral forms rocks in a geological sense, but is properly a compact felspar. It has various' colors and shades, and contains imbedded crystals of felspar and quartz. The name porphyry signifies purple, from iroptyvpa, such having been the usual color of the ancient porphyries ; the same rock exhibits, however, almost every variety of color ; it is the hardest of all rocks, and when polished, Is probably the most enduring. It is much used in Europe for ornamental and architectural purposes ; also for slabs, mortars, and other articles. 392 A POPULAR TREATISE ON GEMS. In the United States, porphyry has never been used for any purpose ; but Professor Hitchcock f emarks, in his Geological Report of the State of Massachusetts, that it would be strange if an increase of wealth and refinement should not create some demand for so elegant and enduring a rock as porphyry. In the same excellent work the author divides porphyry into four varieties, as occurring in Massa- chusetts, in the neighborhood of Boston : 1st. Compact felspar, with several predominating colors; the one with yellow, resembling the Turkey stone; one with red, from brownish to blood-red, closely resembling jasper ; one with a rose-red color, resembling the rose petro- silex of Europe. 2d. Antique porphyry ; closely resembling that European porphyry which was employed by the ancients in monu- ments and ornamental furniture and forms, and is, when polished, a beautiful ornament. It presents numerous vari- eties and shades of color : one of the most elegant is the light-green ; then a deep-green ; red of various shades ; reddish-brown ; black, or nearly so ; gray, and purple ; and the imbedded crystals are usually of a light color, some- times white, brown, and greenish. 3d. Porphyry with two or more minerals imbedded, and having a base of common felspar. This mineral is between sienite and porphyry, resembling the trachytic porphyry, and is generally unfit for ornamental purposes ; the quartz which it contains is hyaline and smoky. 4th. The brecciated porphyry, which is composed of an- gular fragments of porphyry and compact felspar, reunited by a paste of the same material ; the fragments are also of various colors, usually, however, gray and red ; the rock is very hard, and when polished, furnishes specimens of great delicacy for ornamental purposes. Porphyry is much used in England for paving stones, in SEENITE. 393 the entrance halls of large public buildings or private mansions, and the Cornwall porphyry is particularly cele- brated- for its various tints of colors. The author distinctly recollects four slabs : one was a black slab ; another, red ; a third, green; and a fourth, a large slab, containing twenty-four specimens of various variegated rocks of por- phyry. Also, the elvan-stone, from the quarries of New Quay, in Cornwall, which is a beautiful porphyry. The large slab, weighing about eight hundred pounds, was of very fine red color ; it was without flaw or defect. In Prussia porphyry is abundant, and there were some fine specimens in the London Exhibition, such- as a table, a small column and tazza ; the latter was a round slab of red color and fine texture, and the tazza vase and pedestal were of the same material. From Sweden and Norway a sienitic porphyry, of gray- ish-red color, was also in the London Exhibition. The porphyry vase in the Berlin Museum, which, accord- ing to the author's recollection, is about eight feet high and six feet in diameter, is well deserving a place hi this treatise, as it is unique of its kind in the world. SIEXITE. This rock is composed essentially of felspar and horn- blende, and sometimes contains quartz or mica, or both. When polished, it forms the most splendid ornamental stone of all rocks ; it is very hard ; and its color and the mode of distribution of the various ingredients,' make it very agreeable to the eye. It much resembles granite, and is often almost identical with it ; but by close inspection it may be distinguished from the want or addition of the component ingredients. Professor Hitchcock describes six varieties of sienite: 394 A POPULAR TREATISE ON GEMS. 1st. That sienite which is composed of felspar and horn- blende, when the first is white, greenish, and yellowish, and the latter inyariably black. 2d. Felspar, quartz, and hornblende ; the first is foliated, and commonly of grayish, bluish, or yellowish color ; the second from quite light to dark color and hyaline ; and the latter is black. Under this variety the quarries at Quincy and Cape Ann have been arranged by the author (which are generally called granite), on account of the absence of mica. The Quincy granite, or rather sienite, is that cele- brated architectural material used in the cities of Boston and New York, for those huge and magnificent edifices, public as w^ell as private, erected within the last six years ; and it may be supposed that five thousand buildings in the city of New York have been constructed with this splendid article. 3d. Felspar, hornblende, quartz, and mica. This rock, likewise, has a beautiful appearance, but is, as yet, less wrought than the other varieties. The felspar and horn- blende are predominant. The quartz is in small grains, and the mica is black, 4th. Porphyritic sienite ; its base is quartz and felspar, and the hornblende is almost entirely absent ; it has a porphyritic aspect ; the felspar predominates. It is the most ornamental stone when polished. 5th. Conglomerated sienite; it is a quarternary com- pound of felspar, hornblende, quartz, and mica, but all in rounded or conglomerated masses, having the aspect of a pudding-s'tone ; the nodules are from half an inch to six inches in size, and may be easily broken out of the mass, and the hornblende predominates mostly in them. It is unfit for architectural purposes. 6th. Augite sienite ; in this rock the hornblende ia present and rnica absent. It is composed of black horn- SIEXTTE. 395 blende, greenish augite, and yellowish felspar ; all, except the felspar, presenting a crystalline structure; it is also composed only of augite and felspar. The name of the rock sienite was originally derived from Syene, in Upper Egypt, from whence the first specimen was procured ; it was examined and identified by Werner ; many of the Egyptian monuments, such as Cleopatra's Needle, and Pompey's Pillar, were obtained from there. There are valuable quarries of sienite in abundance in the State of New York. It is a durable and beautiful stone, and may be quarried in large' blocks, but on account of its great hardness requires much labor to dress it. Along the North River there are many localities : An- thony's Nose, or Anthony s Face, which is a mountain in the northwest corner of Putnam county, opposite Fort Montgomery. It is called so in consequence of the profile bearing a rude resemblance to the human face, that may be seen in one position, when passing it ; but on account of its steepness, being five hundred feet in height, it is more generally called Breakneck Mountain. Here is the granitic sienite. It is composed of a darkish-gray colored felspar, with a little black hornblende. In Peekskill bay, on the Hudson river, and the adjoining hills for five miles in length, very valuable quarries of this fine rock may be quarried. The sienite rock of the Highlands is veTy extensive ; such as the Target rock on Constitution Island, opposite West Point, and all along the slopes of the mountains in the Highlands, there are boulders and blocks of this valu- able and useful rock. Fort Putnam, near West Point, and the base of Butter Hill, four miles north of West Point, are composed of sienite. When it was ascertained that the famous rock from Syene, in Upper Egypt (so much employed in ancient 396 A POPULAR TREATISE ON GEMS. monuments), and from which the name of sienite was de- rived, was nothing but granite with black mica, and also, that Mount Sinai, in Arabia, was composed of genuine sienite, a French geologist proposed to substitute sinaite for sienite, but the name, although a good one, has never been adopted. The Quin cy and Cape Ann sienite, which is sent from Massachusetts to all parts of the United States, and forms such a beautiful architectural material, is composed of felspar, quartz, and hornblende. GRANITE. This rock is composed of quartz, felspar, and mica, and forms the crust of our globe. It occurs over the whole earth, and the eastern part of the United States is abund- antly furnished with this valuable mineral. As a building material it has been most extensively used for the last ten years ; but the great fire in New York, which, in Decem- ber, 1835, consumed seven hundred buildings, among which about two hundred were of granite, has given a sufficient proof that granite is> in this changeable climate, unfit for a building material, but that it may be usefully employed for ornamental and architectural purposes, where it is not constantly exposed to the atmosphere and weather, which make it so liable to decomposition. Nevertheless, granite continues to be generally employed in the erection of public buildings, warehouses, bridges, &c., and begins to form an important pecuniary object to the merchant and mechanic ; and on this account I cannot forbear to. treat more fully on its general characters, and I must confess that the rich granite treasures of Connecticut, Rhode Island, and Massachusetts, which I had occasion to examine a short time since, on a journey into those regions, GEANTTE. 397 deserve fully all the encomiums bestowed upon them in Hitchcock's Report on the Geology of Massachusetts, and in Shepherd's Report on the Geological Survey of Connec- ticut. So abundant and large are the granite rocks in the eastern part of the United States,* that some single locali- ties are sufficient to supply many countries with this lucra- tive article. Professor Hitchcock divides the granite of Massachusetts into four varieties, viz : 1. Common granite, which, according to him, embraces nine tenths of the granite in Massachusetts : the ingre- dients are a distinct crystalline structure, of mixed and dis- criminating colors. 2. Pseudomorphous granite is that variety in which the mica separates distinctly the other ingredients, which are closely mixed. 3. Porphyritic granite : it contains, besides the usual composition of quartz, felspar, and mica, distinct imbedded crystals of felspar. 4. Graphic granite : this variety consists of quartz and felspar only ; the cross-fracture presents the appearance of written characters. Professor Shepherd divides the ornamental granite of the State of Connecticut into eight different types, viz. : 1. Gray granite. 2. White granite. This variety I have examined myself in Plymouth, Connecticut, and so beautiful was its color and close granular texture, that I took it at a distance for a sandstone, or white marble. 3. Flesh-colored granite. 4. Red granite. * Professor Hitchcock remarks that there is not a town in Massachusetts in which more or less granite does not occur, eiiher as situ or as boulders. 398 A POPULAR TREATISE ON GEMS. 5. Epidotic granite. 6. Porpbyritic granite. 7. Chloritic granite. 8. Sienitic granite. In Rhode Island a fine white granite has, according to Dr. Webb, of Providence, been employed fgr the erection of the arcade of that city, from a quarry in Johnstone, five miles from Providence. The manner in which granite is usually split out at the quarries, is this : a number of holes, of a quadrangular form, a little more than an inch wide and two or three inches deep, are drilled into the rock at intervals of a few inches, in the direction in which it is wished to separate the mass. Iron wedges, having cases of sheet iron, are then driven, at the same time and with equal force, into these cavities ; and so prodigious is the power thus exerted, that masses of ten, twenty, thirty, and even fifty and sixty feet long, and sometimes half as many wide, are separated. These may be subdivided in any direction desired ; and it is common to see masses thus split till their sides are less than a foot wide, and their length from ten to twenty feet. The price of the granite from these quarries, according to Professor Hitchcock, is from forty to forty-five cents per superficial foot, and for hammering and fine dressing it, about thirty cents the superficial foot, such as in the style of the Tremont House in Boston ; common work from twenty to thirty-five cents ; posts for stone fronts cost thirty-four cents per foot. The enterprising citizens of the city of New York have erected gigantic monuments of granite, for future generations to admire. New York abounds in granite, both east and west of the Hudson river, Staten Island, Westchester and Putnam counties. In the city of New York, a large bed of fine granite extends froin. Thirty-first street on the west side, GRANITE. 399 and from Twenty-fourth street in the middle, to Sixtieth street on the north. The Croton Aqueduct is mostly built of granite quarried in Tenth avenue near Forty-eighth street. Granite abounds in Rockland and Orange counties ; it occurs in beds, veins, and irregular masses, forming hills, and often the tops of mountains. The fine-grained varieties of granite are best for eco- nomical uses. When granite contains distinct crystals of felspar, it is called porphyritic ; when the ingredients are blended into a finely granular mass, with imbedded crys- tals of quartz and mica, it is called by French writers, eurite. A granular mixture of quartz and felspar is called pegmatite. In England, Cornwall is particularly celebrated for its granite ; the obelisk from the Lamorran quarries, twenty- two feet high, which was exhibited at the London Exhi- bition, was twenty-one tons in weight, and of a coarse grain, and another, from Cornseco granite, weighing thirty- one tons, and" eighteen feet high, were beautiful specimens of this useful rock. They were each wrought from a single block of granite, and were remarkable for extreme fineness and closeness of grain, and the delicacy of finish which was thereby obtained. The granite column of Cheesewing granite, the property of the Prince of Wales, near Liskeard, in Cornwall, was likewise a magnificent piece. It was thirty feet high. The bust and pedestal of blue Peterhead granite was also an interesting specimen of its kind. Swedish granite has been known for many centuries ; it is obtained from extensive quarries on the island of Ma- leuva, on the west coast of Sweden. It bears a high polish 400 . A POPULAR TREATISE ON GEMS. PEARLS. Pearls are concretions, consisting of carbonate of lime, having a roundish, tubercular, or angular form ; a white, gray, blue, or green color ; a shining lustre, and the hard- ness of lime; specific gravity, 2*68. They are found in several bivalve shells the meleagrina margaritifera, haliotis gigas, and haliotis iris, and a large species of turbo, which shells are known in commerce as flat shells, ear shells, green snail shells, buffalo shells, and Bombay shells ; many unios, alaniadontas, &c. Mother of pearl is the internal or nacre- ous layer of such shells. These precious substances are the result of an excretion in superimposed concentric laminae of a peculiarly fine and dense nacreous substance, which con- sists of membrane and carbonate of lime. The finest qual- ity is produced by the bivalve of the Indian seas, called par excellence the pearl oyster (meleagrina margaritifera}. In the United States the alasmadonta arcuata, corresponding with the mytilus margaritiferus of Barnes, the unio ochra- ceus, unio complanatus, and many other species, contain the pearls, and according to the nacre of the shells the color of the pearl is corresponding. The origin of pearls is by some considered to be unfructi- fied eggs ; by others, a morbid concretion or calculus, produced by the endeavor of the animal in the shell to fill up holes therein ; by others again, as mere concretions of the juice of which the shell has been formed, and with which the animal annually augments it. It is very plausi- ble, however, that the animal of the shell is attacked often by enemies, such as the boring shells (turritella), &c. ; that grains of sand, or any other pointed substance, which, on such occasions, come within the shell, stick fast and aug- ment with the growth of. the shell; it is also known that pearls may be produced artificially, by pressing a sharp PEARLS. 401 body on, or by boring a hole in, the shell. The Chinese are in the habit of laying a string with five or six small pearls separated by knots, inside of the shells, when the fish are exposing themselves to the sun, and taking them out after some years, whereby they obtain very fine and large pearls, and but a little open on the side where they were adherent to the shell. The pearl fishers say that when the shell is smooth and perfect, they never expect to find any pearls, but always do so when it has begun to be deformed and distorted. It was therefore concluded, that as the fish grew old, the vessels containing the juice for forming the shell and keeping it in vigor, became weak and ruptured, and from this juice accumulating in the fish, the pearl was formed, and the shell brought to decay, as supposed by M. Reaumur. It would be, according to this idea, a sure guide to know from the form of the shell, whether the pearl is large or small; and thus by the smaller ones being thrown back into the sea, a constant crop of large pearls might be obtained. The mother-of-pearl fish is found in the East and West Indies, and other seas in warm latitudes, and in the rivers of north and middle Europe. In some parts of the globe, they are found in clusters, containing a great number; the places where found are caUed pearl- banks. The most famous are near the coast of Ceylon, that of Japan, and in the Persian Gulf, near the island of Bahreim ; also near the coast of Java, Sumatra, &c. The finest and most costly pearls are called the Oriental, and are from the above places ; they are all white or yellowish ; those from, the Persian Gulf, on account of their perfect whiteness, are preferred to those from Ceylon. Pearls are collected in rivers with the hand, but in seas it is the busi- ness of divers, brought up to this most dangerous occupa- tion from early youth. In the East Indies there are two seasons for pearl fishing ; the first in March and April, the 402 A POPULAR TREATISE (N GEMS. second in August and September ; and the more rain, the more productive are the pearl fisheries. In the beginning of the season there are sometimes two hundred and fifty barks on the banks ; the larger barks have two divers, the smaller, one. The divers descend from their barks with a rope round their body, and a stone of twenty or thirty pounds attached to one of their feet, so that they may sink speedily from eight to twelve fathoms, where they meet the shells fastened to the rocks ; the nostrils and ears are stuffed up with cotton, and to the arm a sponge dipped in oil is fastened, which the diver now and then brings to his mouth, in order to draw breath without swallowing water. He also carries down with him a large net, tied to his neck by a long cord, the other end of which is fastened to the side of the vessel, to hold the shells, and the cord is to draw him up when the net is full, or when he wants air ; he has likewise a knife or an iron rake, for detaching the the shells from the rocks. Thus equipped, he precipitates himself to the desired depth, where he can very distinctly see all that is passing around, yet cannot escape in time the sudden approach of sharks, to whom he too often becomes a prey. When the diver has been in water some minutes, and has his net filled, or is unable to stay any longer, he loosens quickly the stone at his foot, shakes the line, and he is drawn up by his companions. The diving-bell is now frequently used ; more so than in former years. In the Persian Gulf the divers rub their bodies with oil, and fasten a stone of about fifty pounds to their feet. The shells obtained are piled up in heaps, and left ex- posed to the rain and sun until the body of the animal putrefies, and they open of themselves. Those containing any pearls have from eight to twelve. After being picked out, washed, and dried, they are passed through nine sieves of different sizes. PEARLS. 403 At the Pearl Islands, near the Isthmus of Panama, the pearl fisheries have, within a few years past, become a lucrative business to many of the inhabitants. The clivers use more simple methods than those we have mentioned, for collecting the pearl oysters : they traverse the bay in canoes that hold eight men, all of whom dive naked into the water, from eight to ten fathoms deep, where they remain about two minutes, during which time they collect all they can with their hands, and dexterously rise to- deposit them in their canoe, repeating the operation for several hours. In Sweden, the pearl oyster is caught with a pair of long tongs. The fishermen are in small boats, painted white on the bottom, which reflects the light to a great depth, and as soon as they perceive them passing under- neath they seize the oyster. Pearls are esteemed according to their size, form, color, and lustre ; the largest, of the size of a small walnut, are called paragons, which are very rare ; those the size of a cherry, are found more frequently, but still are rare ; they are the diadem or bead pearls. They receive names, also, according to their form, whether quite round, semi-circular, and drum-form, or that of an ear-drop, pear^ onion, or as they are otherwise irregularly shaped. The small pearls are called ounce pearls, on account of being sold by weight, and the very smallest, seed pearls. Those of a brilliant white color, or white water, are most sought for in Europe ; those of a yellowish color in some parts of Asia ; and some of a lead color, or those of a jt black, are preferred among some nations. They all turn more or less yellow with age, and to restore the white color, they are either baked in bread, rubbed with boiled salted rice, or kept for a short time in the gastric juice of fresh-killed chickens. Pearls are sold by weight troy weight j but the penny- 404 -A POPULAR TREATISE ON GEMS. weight of twenty-four grains is counted as thirty ; so that an ounce has six hundred grains, pearl weight, and four troy grains are equal to five pearl grains. The price has, within the last forty years, much diminished, for two reasons : 1st. Diamonds, and particularly brilliants, have become more plentiful, and have since been worn, not by the higher classes alone, but also by the middling. 2d. Within the last twenty years, artificial pearls have been manufactured in high perfection, and are worn to a great extent. It is my opinion, however, that the price of pearls will take a fresh rise among the nobility and richer classes, diamonds being now so generally worn ; as persons, think- ing to invest safely, without any future loss, their surplus capital, purchase brilliants that formerly were possessed exclusively by the rich. Pearl fisheries were first carried on in remote times in the Persian Gulf, and the most celebrated, formerly, were near the island Bahreim. Five hundred thousand ducats was then the yearly produce. About one million dollars' worth, at the present time, are exported. The island Kharack now produces the most considerable quantity. The principal market is at Muscat ; from thence they are brought to Surat. The mode of procuring them pursued in those countries, is in canoes, holding fifteen men, six of whom are divers: the shells caught during the day are delivered to a surveyor* when they are opened on a white cloth, and whoever finds a pearl of some value, puts it in his mouth, to give it, as they say, a " better water." The greatest harvests are generally after many rains, and the largest pearls are mostly found in the deepest water. At Ceylon the pearl fisheries are now considerable, particularly in the bay of Condatchy. The shells are there left to PEARLS. 405 reach the age of seven or eight years, and in the fourth year they have small pearls, sometimes a hundred and fifty. They fish yearly, in the month of May, during four weeks. In the year 1804, eight hundred canoes, each with two divers, were engaged. Before the year 1800, the pearl banks were leased, to an Indian merchant, for three hun- dred thousand pagods ; and before the arrival of the Euro- peans in India, the same bank was used every twenty or twenty-four years ; when under the Portuguese,.every ten, and under the Dutch, every six years. In 1800, the produce was from one hundred to one hundred and fifty thousand pounds sterling. Japan has some pearl banks, which are, however, not much sought ; the same may be said of the Nipthoa lake, in Chinese Tartary. America sent, in the sixteenth century, pearls to the amount of eight hundred thousand dollars to Europe. The shells were mostly collected from Cape Paria to Cape Velo ; round the islands Margarita, Cubagua, Coche Punta, Aragy, and at the mouth of Rio la Hacha," from which latter locality, and the Bay of Panama, Europe is now mostly supplied. The former localities have long since been relinquished, on account of their small produce ; too many shells having been removed at one time, thereby retarding the growth of pearls. Panama has sent, within a few years past, about one hundred thousand dollars' worth of fine pearls to Europe, the trade being carried on by Messrs. Plise, of Panama. The coast of Florida is said to have been vefy lucrative to the Indians, as a pearl fishery, which, however, does not prove so now, since the settlement of civilized people. England used to be supplied from the river Con way, in Wales ; and Scotland supplied the London market, between the years 1761 and 1764, to the amount of ten thousand pounds sterling ; but the supply has failed. Pearls are 406 A POPULAR TREATISE ON GEMS. found in the Elster river, in the kingdom of Saxony, from its source at the borders of Bohemia to Elsterberg, where the fishery has been jcarried on since 1(521, with some ad- vantage to the sovereign ; some pearls found there were valued at fifty Prussian dollars each. In the river Watawa, in Bohemia, and in the Moldau river, from Kruman to Frauenburg, pearls are found of great beauty; so much so as to equal in price the Oriental pearls. Also, at Rosenberg, pearls are* sometimes found superior to the Oriental in lustre ; and at Oelsnitz, a considerable pearl fishery is car- ried on. Most of the rivers in Sweden, Lapland, Finland, Poland, Norway, Jutland, Silesia, and other places, contain pearls, but they are not collected. It is a "fact that the pearl is equally hard throughout all . its concretional layers, for by putting the pearl in a weak acid, the outside layer becomes gelatinous, arid the suc- ceeding layers are found to be equally hard and uniform. It is almost impossible, therefore, that the story told of Cleopatra having swallowed a pearl after being dissolved in vinegar, should be true ; besides, if the pearl had been dissolved as quickly as reported, it would not have made a very disagreeable beverage. Pearls were known, and were very much esteemed by the Greeks and Romans, and when they became acquainted with the Indies, by com- mercial intercourse and conquest, they preferred the pearls of the East to those that were obtained from the rivers of Europe, or even from the Mediterranean. With the ancients the wearing of this species of curiosity became a passion and even a folly. Necklaces, bracelets, and ear-rings were then worn in profusion ; dresses, head and foot ornaments were manufactured with pearls. Mil- lions of sesterces (a Roman coin of two hundred francs value), were expended and lavished for the best and most extraordinary pearls. The two pearls of Cleopatra cost PEARLS. 407 nearly two millions of francs ; Julius Caesar presented to Servilia, the sister of the celebrated Cato, of Utica, a pearl which he purchased for one million two hundred thousand francs-. Lollia Paulina, the wife of Caligula, wore ornaments to the value of eight millions of francs. The ladies went so far as to ornament their buskins with pearls. Nero lav- ished pearls upon his lewd women. In modern times Buckingham distributed in the halls of the Empress Ann, of Austria, and of King Louis XIII., pearls to the value of three hundred thousand francs. The baroques, which are excrescences in the mother of pearl, are sometimes very large, and display some extraor- dinary figures and inconceivable freaks of nature. They are held in high estimation, and are mostly worn in Spain and Poland. Caire, the celebrated French jeweller, possesses many baroques ; one representing a bearded dog ; another, rep- resenting the order of the fleece. " He had a mother of pearl containing a large excrescence, representing a Chinese with crossed legs. The prices of pearls, from one carat upwards, were for- merly determined like those of diamonds, viz : if the carat b fixed at five dollars, and a pearl weighs four carats, take the square, or sixteen, which multiplied by five is equal to eighty; so that a pearl of four carats was estimated at eighty dollars. At present the following are the prices of pearls : 1 grain is worth, in France, 4 francs per carat. 9 K c |0 it " 3 " " " 25 " u 4 " (1 carat) " 50 " " The baroque pearls are sold at from three hundred to one thousand francs per ounce. 408 A POPULAR TREATISE ON GEMS. The seed pearls, when quite round, are worth about one hundred and twenty francs per ounce. In France, perforated pearls are valued at twice the prices given above. The piercing of the pearl is well un- derstood in the Indies. The value of a pearl is always enhanced by size, perfection, and color ; those that have a yellowish-white, or silver-white, or very pale gold-yellow shade, or a rose or lilac color, are the most esteemed pearls. The French pearl fisheries produce at least from three to four millions of franco. The French Crown possesses pearls of immense value : One round virgin pearl, of a magnificent orient, weighing, 27 T 5 g- carats, is valued at two hundred thousand francs. Two pear-shaped pearls, well formed, of a beautiful orient, and weighing together 57y^ carats, are valued at three hundred thousand francs; two ear-drops, weighing 99 T 6 ^ carats, are valued at sixty-four thousand francs. About seventy-two more large pearls, of great beauty and exquisite form, pear-shaped and round, valued in the aggregate sum of three hundred and fifty thousand francs. At the Paris Exhibition, in 1855, an enormous pearl, of pear-shape, brought from Berlin, by Napoleon I., was exhibited. The Princess Royal of England, at her marriage to Prince Frederic William, of Prussia, .wore a necklace of the finest pearls, which cost, at the least calculation, five hundred thousand francs. The Emperor Rudolph possessed a pearl weighing one hundred and twenty grains. King Philip II., of Spain, possessed a pear-shaped pearl of the size of a pigeon's egg, weighing one hundred and thirty-four grains. It came from Panama, and was valued at fifty thousand ducats. It was called the Peregrina. PEAKLS. 409 In 1620, King Philip IV., of Spain, purchased a pear- ehaped pearl from Gougitas, of Calais, which weighed four hundred and eighty grains. An anecdote is told of the King, who asked the merchant how he could risk his whole fortune in so small a piece as that pearl ; whereupon the merchant replied, that he knew there was one king of Spain in the world who could afford to purchase it. It now belongs to the Princess Youssopoff. A costly collection of pearls from the Indies, Ceylon, and Singapore, and innumerable pieces of ornamental jew- elry set with most costly pearls, was exhibited at the Lon- don Exhibition by Messrs. Garrard, Hunt, Roskell, and other jewellers. A large pearl, from Vermont, United States, weighing eleven carats, and very round, but not of bright color, is in the possession of Mr. S. H. Palmer. Messrs. Blogg & Martin, of London, inform me, under date of April 25, 1859, that they have in their possession a magnificent pearl necklace, consisting of thirty-seven per- fect pearls, of forty grains each ; they sent a description of it, and also of two beautiful pearl-drops, which they value at two thousand pounds sterling. The necklace and drops, which must be unique specimens, deserve more than "a mere notice, but the description came too late for insertion. United States Pearls. New Jersey merits the credit of producing fine pearls ; a great many thousand pearls have been obtained from the mussels, which compare fairly with those of the India pearl- shell ; size, color, nacre, and orient are displayed in many of the New Jersey pearls in a high degree, and are now passing in Europe for the genuine Oriental or Panama pearls. In 1857, a shoemaker named David How ell, living 18 410 A POPULAR TREATISE ON GEMS. Fig. 14. PEAHLS. 411 Fig. 12 J. Fig. 15. Fig. 16. 412 A POPULAR TREATISE ON GEMS. near the town of Paterson, New Jersey, went to a neighbor- ing brook, called Notch brook, in order to collect some mussels for his breakfast, and, on opening them, discovered a great many loose pearls falling out, which he took to a jeweller in Paterson, who stated to him that they were valuable, and they both began to collect millions of these mussels, and their efforts were crowned with success. The preceding representation of the mussel belongs to the great family of unio, which was formerly called the avicula mar garitifera, mya margaritifera, but now known as an alas- madonta arcuata named by Barnes. Many unios (of which there are, according to Lea, Say, and other Ameri- can conchologists, over six hundred species), contain pearls more or less ; and Mr. John H. Redfield, the efficient corresponding secretary of the New York Lyceum of Natural History, informs me that he found the pearls in the same locality in New Jersey, in three or four other unios, such as the unio complanatus, unio ochraceus, unio radiatus, &c. A very perfect pearl in the shell may be seen in the annexed drawing, which is copied from " Frank Leslie's Illustrated News" of May, 1857; the pearl is rather dark, and the shell, as may be seen, appears worn off. This is one of the characteristics of the shells containing pearls, and it appears to indicate that the animal is in the decline of life, and that the mussel is becoming gradually decayed. The streams in which these pearl shells are found are generally very shallow, not more than one or two feet deep, and the shells may be picked up with the hands; many thousand shells are opened, containing deposits of the pearly matter, most of which contains shapeless and colorless pearls^ which are so small that they -are of no value ; many, however, contain very perfect pearls ; the crown-pearl, weighing ninety-one grains, in the possession PEARLS. 413 of Messrs. Tiffany & Co., was purchased from Mr. Howell for $1500. This pearl resembles a crown, having three smaller pearls resting upon the large pearl ; another repre- sentation of a pearl weighing nearly four hundred grains, here represented, was destroyed by cooking the mussel in. order to open it better, and the color of the nacre has been spoiled ; it would, probably, have been the largest pearl of modern times, and of immense value. The alasmadonta of the present day was formerly called mya, from the Greek fiva), to compress, it is called in English, the gaper, on account of the bivalve gaping at one end, its hinge having a solid, thick, patulous tooth, seldom two, and not inserted in the opposite valve; the same genus was originally called mytilus; they inhabit both the ocean and fresh water; they perforate the sand or mud at the bottom. Many species are caught for food, and others for the pearls; some few of the same genus perforate and live in limestone, like the pholadites. The pearl-bearing mya, now alasmadonta, is frequently found in the large rivers of northern latitudes. The Brit- ish Islands, especially Ireland, were formerly famous for their fisheries, and a few pearls of great value have at times been obtained from these sources, although the British specimens are not held in high estimation, with the excep- tion of a few procured from, the river Shannon, in the year 1821. The river Irt, in Cumberland, the Conway, in Wales, and the Tay, in Scotland, were once noted for their pearl fisheries. Suetonius reports that Caesar was induced to undertake his British expedition for the sake of the pearls ; and according to Pliny and Tacitus, he brought home a buckler made with British pearls, which he dedicated to, and hung up in the temple of the idol Venus genetrix. The gapers are mostly used for food, both in Britain 414 A POPULAR TREATISE ON GEMS. and on the Continent ; around Southampton, in England, these mussels are known by the whimsical name of " old maids," and the inhabitants of the northern islands call them smuslin, and consider it a fine supper-dish, which is by no means unpalatable.* I am informed by Mr. Plise, who brought a considera- ble quantity of pearls from Panama, that he receives four dollars per grain in England, for those of good size and quality. Pope Leo bought a pearl for eighty thousand crowns. Tavernier describes one belonging to the King of Persia, which is said to have cost one million six hundred thousand livres. Portugal has a pearl in her treasury of the size of a pear. Two Greeks, residing in Moscow, are in posses- sion of a pearl weighing twenty-seven and seven eighths carats. For restoring Oriental pearls to their original lustre, which they lose in the course of time, the following pro- cess is resorted to in Ceylon : the pearls are allowed to be swallowed by chickens, which are then killed, and the pearls are an hour afterwards taken out of the stomach, when they are as white and as lustry as if just taken from the shell. The poet Cowper thus expatiates on the mussel: " Condemn'd to dwell Forever in his native cell ; Ordain'd to move where others please, Not for his own content or ease ; But toss'd and buffeted about, Now in the water and now out ; Yet in his grotto-work inclosed He nothing feels in that rough coat, Save when the knife is at his throat; Wherever driven by wind or tide, Exempt from every ill beside." PEAELS. 415 Artificial Pearls. Artificial pearls or beads are of various kinds; most generally they consist of solid masses of glass, with a hole drilled in them ; or they are blown hollow, and then filled out with metallic lustry grains, wax, or with the fine scales of the bleak fish, which have a silvery and pearly lustre. The art of imitating pearls is attributed to a manufac- turer of beads, of the name of Janin or Jalquin, who lived at Paris in 1680; he was led to the discovery by seeing, one day, the scales of the bleak fish swimming in a trough, where the fish detached them by rubbing against each other, and he at once conceived the idea of applying these scales for imitating the orient of the pearls, by mixing them with a mucilage and filling the interior of hollow glass bulbs, and he gave this natural and wonderful pro- duction the name of Extract of Orient a very singular name, but still significant of the meaning of its employment. It is well known that this little white fish, the bleak, is found in abundance in the rivers Seine and Marne, in France, and in many small rivers in Sweden, Germany, and Italy. The bleak fish fructifies around water-mills, where they are caught by nets. For the purpose of extracting the color of the scales of the fish, they are rubbed pretty hard in the fresh water collected in a stone basin, which settles down in the bottom of this vessel ; the sediment is then pressed out through a linen rag, and they are then replaced again in fresh water and left there to settle for several days, when the water is drawn off and the precipitate is carefully collected ; this is called the extract or essence, and it requires from seventeen to eighteen thousand fishes to obtain five hun dred grammes (a little over one pound). The scales being animal matter are, therefore, liable to 416 A POPULAR TREATISE ON GEMS. decomposition, and for their preservation numerous chemi- cal agents have been employed by the different manufac- turers, all of whom, who have succeeded, keep it a secret ; it is, however, known that liquid ammonia is added to the paste of the scales. . The operation of the manufacture is very difficult, but an experienced workman can manufacture six thousand pearls in a day. The chemists have experimented for some years to imi- tate the extract of orient, as it requires such a large quantity of fishes to obtain any amount of the scales, and according to Mr. Barbot, the following preparation has produced a favorable result : which is by distilling one part of oxide of bismuth and two parts of corrosive sublimate ; the product is a species of butter, which on redistilling yields metallic quicksilver and a very fine powder ; this is the substance used for orientalizing or coating the artificial pearls with the true gloss- of an Oriental pearl. The same scales are likewise used to coat beads of gyp- sum, or alabaster, which are soaked in oil and then covered with wax to give them a pearly appearance. The Roman beads are made in this manner : the scales are dissolved either in liquid ammonia,- or vinegar, and the solution or liquid is used for covering those artificial beads. The Turk- ish rose-beads are made of an odoriferous paste, and are turned afterwards like those of coral, amber, agate, or other hard substances. The knitting beads are sold in meshes of one hundred and fifty, or twenty strings, of fifty beads each, of various colors ; and the large glass- beads in meshes of twelve strings. There are numerous manufactories in Germany and Italy of the various kinds of beads, which are used to a very great extent both in Africa and North and South America. Germany exports yearly from its different manufacturing places, such as PEARLS. 417 Heidelberg, Nuremberg, Sonnenberg, Meistersdorf, in Bo- hemia, and Mayence, more than a million dollars' worth. In Venice are large establishments for the finest cut beads. Nuremberg manufactures, besides glass beads, consid- erable quantities of amber beads. In Gablontz, in Bohe- mia, more than six thousand persons are engaged in the manufacture of beads, that are made of pure glass, or of a composition. From the glass-houses, which are very numerous in Bohemia, the rods of different sizes are delivered to the glass mills for cutting, which is performed by water power or by hand. In 1828 there were in that neighborhood one hundred and fifty-two mills in operation; a number of glass-blowers were likewise engaged, who possessed great dexterity in blowing the small beads with the assistance of a small blow-table. In the manufactory of George Benedict Barbaria, at Venice, six hundred varieties of beads are constantly making ; and that of Messrs. Gas- pari and Moravia manufactures, besides the beads, every article of jewelry from the same material. The rose beads of Steffansky and Tausig, are made of bread crumbs, which are beaten up with rose water in a wooden mortar, until they become a uniform mass, to which is added some otto of roses and drop-lake, when it is made into beads with dissolved gum tragacanth ; for the . black rose-beads, Frankford black is substituted hi the place of the drop-lake. Lamaire, of France, manufactures beatfs equal in lustre and beauty to real pearls. He adds to 1000 ounces of glass beads, 3 " scales of the bleak-fish, ^ " fine parchment glue, 1 " white wax, 1 " pulverized alabaster, with which he gives them an external coating. 18 418 A POPULAR TREATISE ON GEMS. Rouyer manufactures his beads, also in France, from opal, which he covers with four or five layers of dissolved isinglass, and then with a mixture of a fat oil, spirits of turpentine, and copal, so as to prevent their becoming moist. In order to render them of the peculiar lustre of the Oriental pearls, they are covered with a colored enamel. The opal is fused into rods by a lamp, over which is laid a brass wire to support it ; the wire is held in one hand and the opal in the other, and the wire is then kept turning until the bead has the desired size and .roundness; if a colored enamel is to be applied, the beads are made but half the required size, which being done, they are once more covered with the opal, then the solution of isinglass is used, and lastly the varnish. Beads made in this man- ner are with difficulty distinguished from the Oriental pearls. The best method of making artificial pearls, is certainly by means of pulverized real pearls. Either the smallest, or the deformed large specimens, may be reduced to a fine powder, and then soaked in vinegar or lemon-juice, and the paste made up with gum tragacanth ; they may then be cut out with a pill machine, or a silver mould, of any desired size, and when a little dry, inclosed in a loaf and baked in an oven : by tin amalgam, or by the silver of the scales of young fish, the proper lustre may be given. The artificial pearls, by Constant Vales & E. Truchy, of Paris, which were on exhibition in the London Crystal Palace, were extremely beautiful, and were with the greatest difficulty distinguished from the natural pearls. Messrs. Bouillette, Hyvelei & Co., of Paris, exhibited, besides many beautiful pearls, a great variety of artificial stones, all of their own manufacture, and very tastefully set ; among them was a stomacher in diamonds, pearls, and emeralds. CORALS. 419 The shad-fish, as well as the white-fish of our lakes, must yield an extract of orient, of as good a quality as the bleak- fish of the Seine, and it is to be hoped that some enter- prising mechanic may take an opportunity of preparing the white matter adhering to the scales of the fish just men- tioned, either for export, or for the purpose of imitating pearls, which may be done as well in this country as any- where else. The usual price of false pearls is two dollars and fifty cents a string, one hundred to the string ; but some are lower, and some higher, according to color. CORALS. Corals are zoophytes, whose calcareous habitations resem- ble vegetable branches. They live in the sea, adhering to rocks, stones, or vegetables, and shoot to the surface of the water in tnbiform stems with branches, generally coated with a gelatinous or leathery skin that incloses a cartilagi- nous marrow, composed of many cells, inhabited by the animals, who propagate in sprouts from eggs so fast, that small reef-rocks are formed, which in the course of time become islands. The red coral, or precious coral (iris nobilis), belongs to that family of zoophytes which live mostly in the cavities of rocks in the sea ; the stem is always of a beautiful red color, rarely white ; quite compact, striated on the outside, of entire calcareous composition ; it grows one foot high and an inch thick. The stem is covered with a leathery crust, containing open warts of eight teeth, in which the animals, or polypi, with their eight arms, are situated ; the arms are whimpered, and the animal grows very slowly. The red coral is fished up with nets of strong ropes, fas- tened on large wooden cross-beams, which are thrown 420 A POPULAR TREATISE ON GEMS. down on the places where the corals are known to be fas- tened, and an expert diver contrives to entangle the nets in the reefs, which are then drawn up by force. The corals so brought up are cleaned, assorted, and sold to the manu- facturers. Messrs. Payenne & Laminal have invented a very inge- nious machine for collecting the coral from the banks of the ocean, without breaking the fine branches and without injuring the banks which are formed for the growth of the coral. It is a fact admitted by naturalists and fishermen, that the growth and accumulation of the zoophytes take place continually in the same waters ; and that as great and pro- lific a traffic may be created by coral catching as by the fish- eries in France. Lord Ellis proved, in 1754, that the coral polype possesses an ovarium filled with small eggs, pre- pared for hatching ; all these eggs are attached together by a species of cordon, and resemble worms ; tentacles are shooting out from them, which move in the same manner a$ the grown polypes. In 3856, Mr. Focillon presented a report to the Acclimi- tation Society at Paris, on the methodical exploration of the ancient and natural banks, and on the construction of artificial coral banks in such a manner as to secure the most favorable position for the production and operation of an easy and sure coral harvest. Facts have already been elicited, that the new coral succeeds so well at a depth of seven to eight metres (twenty four feet), under the influence of the rays of the sun, that it develops quickly, and becomes large and of good color at the end of eight or nine years; while a coral at a depth of thirty to fifty metres (one hundred and fifty feet), requires from thirty- five to forty years to shoot out, and it is not then of as good a color as the former. This discovery ought to COEALS. 421 stimulate the African coast (Algeria), particularly the in habitants on the shores of Bona, Oran, and other places, who ought to be beforehand in the application ; also on the Marseilles coast, which is already full of coral reefs. . Coral was formerly cut in facets, and was in great favor under the consulate and empire of France, for almost every species of luxury ; combs, ear-rings, necklaces, beads, crosses, &c., were manufactured and sold at high prices ; but the fashion and price soon fell. Ten or fifteen years after- wards an endeavor was made to bring coral in vogue again, by offering coral engraved as cameo, and made into other ornaments, such as brooches, bracelets, ear-rings, and pins, which were then sold pretty high ; but on account of an insufficient supply of the article and bad workmanship, it fell back to its original lethargy, and for many years it was considered worthless and altogether out of fashion. During the last two years, coral has resuscitated very much, and got into good grace with the ladies. The Parisians have, however, changed their taste for the former favorite, the red coral ; the rose-colored, cut in a round form, so as to nearly resemble a rose pearl, being preferred, which is acknowledged to be extremely rare. The price of these rose'-colored corals has of late risen so high, that a fabulous sum is paid for them; and a coral which was worth but fifty francs in 1810, is now sold for three hundred francs and upwards. At present the fashion for corals is at its height, and ornaments of every con- ceivable variety may be seen in the shops of jewellers in this country, imported from France and Italy. . At the last Paris Exhibition there was a coral chess- board, with all its figures representing an army of Cru- saders and of Saracens, which was admirably executed, and valued at 10,000 francs. Coral branches, if. without a frac- ture, bring a great price. 422 A POPULAR TREATISE ON GEMS. France manufactures and exports coral ornaments to the value of six millions of francs, and the demand for them is much greater; the establishments of Barbaroux and Garaudy & Fils, in Marseilles, where the coral is principally- manufactured into ornaments, give proof that France will retain the supremacy in this species of luxury. In the Paris Exhibition of 1855, many curious sculptured and chiselled objects were shown by Arsene Gourdin, of Paris. In the London Exhibition, fine corals were shown from the Cape of Good Hope, from Reftaelli & Son, in Tuscany; from Algiers .was also a collection. Tucker & Co., of Ber- muda, exhibited a fine collection of both corals and madre- pores, including the black flexible coral (gorgonia). Among the ancient rare coral engravings is the head of the philosopher, Chrysippe, in high relief: it was in the Orleans collection. A coral cameo of the 14th or 15th century, representing a Sphinx with three Cupids, well executed, is mentioned by Caire. The red corals are distinguished by the names of the countries where found. 1. The Barbarian, which are the thickest and purest. 2. The Corsican, which are the 'darkest, but not so thick, and less pure. 3. The Neapolitan, and those from Ponza, which are clear and pretty thick. 4. The Sardinian, which are thick and clear. 5. The Catalonian, which are nearly as dark as the Cor- sican, but mostly thin. 6. The Trapanian corals, from Trapani, in Sicily, which are somewhat preferred at Leghorn. The darkest corals are most liable to be worm-eaten. The polished corals are generally sold in bundles, which consist of a certain quantity of strings, of a certain weight. CORALS. 423 They are strung in Leghorn, either of various or equal thicknesses, which latter are then of various sizes, and the bundles receive their names accordingly; grossezze, mez- zanie, filotti, capiresti, &c. The thickest corals are put up in one string, resembling a tail, and are called codini ; the smallest are called smezzati. At Genoa, the various large corals are called mezza- nie j the uniform large, filze / and the uniform small, migUari. They are distinguished according to color at Leghorn ; the darkest red are called arcispiuma, Avhich are the dearest ; and then primo, secundo, terzo, quarto, coloro or sangue, chiari, moro, nero, &c. According to form they are called round (tondi), and cylindrical-round (boticelli). The former are sent to all parts of the world, but the latter are only sent to Poland. The large boticelli are put up in meshes of twelve pounds, containing thirty-six strings ; and the middling size of the boticelli are in meshes of six pounds, containing sixty strings; those boticelli which are still larger, are called olivatti, and are only sent to Africa ; those which are glob- ular, and not drilled, are called paUini altorni, and sent principally to China, where the favorite color is the rose- red. The sound corals are called netti, and the worm-eaten, camolatti, which latter are mostly sent to the East Indies. The tops of the branches are called dog-teeth, or dents canines, and the thick ends of the branches are called mao- metti both kinds are perforated lengthwise, and are used in Barbary as ornaments for horses. The fine large coral stems which form suitable specimens for cabinets of natural history, in Marseilles, are called chouettes. There are one hundred varieties of shades of red coral distinguished at Marseilles. 424 A POPULAR TREATISE ON GEMS. Corals are principally used for ornaments, in the East Indies, China, and Africa, where they are preferred to the diamond. Almost every East India lady wears a bracelet or necklace of corals. The white coral has its origin from the eight-star coral (rtiadrepora occulta)] and the black coral from the black- horned coral (gorgonia antipotlies) . The medusa head (caput medusce), called the sea polen, belongs likewise to the coral family, and consists of sixty-two thousand six hun- dred and sixty-six articulated members. Corals are fished for on the coast of Barbary, between Tunis and Algiers ; in the latter state Bona is the principal station ; the French have one also at Basteon de France. The monopoly was purchased by France, in the seven- teenth century, at eighteen thousand dollars annually; and by England, since 1806, for fifty thousand dollars. At Bona there is a summer fishery, from the first of April to the first of October, which occupied, in 1821, thirty French, seventy Sardinian, thirty-nine Tuscanian, eighty-three Neapolitan, nineteen Sicilian barks ; alto- gether, two hundred barks of two thousand and twenty- three tons capacity, with two thousand two hundred and seventy-four men ; they fished up forty-four thousand two hundred pounds of coral, valued at two million four hun- dred thousand francs. The winter fishery of the same year occupied three French barks, each with nine men, and they obtained six hundred and eighty pounds of coral. The principal manufactories of corals are now at Leg- horn, where this branch of business has been carried on for two hundred years past, by the Jews. There were for- merly twenty establishments, but the number has lately been much diminished. They are sent principally to China, the East Indies, and Arabia, partly by the way of London, and partly by Mos- SHELL CAMEOS. 425 cow, Aleppo, and Alexandria; many corals are likewise sent to Poland. Genoa has a few manufactories, in which the Sardinian corals are mostly wrought. At Marseilles there has been a large manufactory ever since 1780, and at present it is the only establishment of the kind in France. The East Indies consume, according to the statement of Le Goux de Haix, nearly four million francs' worth. Corals are worn in the East as ornaments in the turban, and the Arabs bury the coral with their dead. A large coral, from the manufactory at Marseilles, was sold in China, to a mandarin, for twenty thousand dollars. Purpurin is the name of artificial coral. A large quan- tity of this false and base imitation of coral has been im- ported into this country. It is used for setting in cheap jewelry; brooches, bracelets, ear-rings, and pins may be seen everywhere in this city, all carved in figures and ani- mals, resembling the true coral, but on testing it with a knife, the baseness is easily detected. It is composed of marble powder, made into a paste by a very siccative oil or varnish, or soluble glass (silicate of potash), and a little isinglass, and colored by Chinese vermilion. The paste is then moulded into the various objects required, and when dry such parts as require it are perfected with the chisel. SHELL CAMEOS. The shells employed for cameo-cutting, .are the cassis rufa, and several species of cyprea, called cowries. They are dense, thick, and consist of three layers of differently colored shell material. In the cassis rufa, each layer is composed of many very thin plates, or lamina?, which are perpendicular to the plane of the main layer ; each lamina consists of a series of elongated prismatic cells, adherent by 426 A POPULAR TREATISE ON GEMS. their long sides ; the laminae of the outer and inner layers are parallel to the lines of growth, while those of the middle layer are at right angles to them. In cowries there is an additional layer, which is a duplicature of the nacreous layer, formed when the animal has attained its full growth. At the London Exhibition there was a very fine collec- tion of shell cameos, from Rome, owned by the engraver Seculine. Certain natives of India prepare shell cameos with rude but efficient instruments for cutting them, and the Indian department in the Exhibition showed numerous specimens. MOSAIC AND PIETRA DURA. Roman, Venetian, Florentine, and other Mosaics. The art of mosaic (opus musivum of the Romans), was origi- nally applied only to the combination of small dice-shaped stones (precious and common), or tessera? of the ancients, in patterns. It has long been an important source of labor to the inhabitants of several parts of Italy, such as Venice ; and under various modifications is now carried on in the principal cities of Europe. The manufacture has long ceased to be confined to combinations of tessera?, and is now understood to include all kinds of inlaid and veneered work, in whatever material, fragments of pseudo-precious stones (agate, chalcedony, malachite, lapis lazuli), marbles of the most variegated colors, porphyry, lava, granite, fluor-spar, and also the various colored glasses (imitation gems), avanturine, and enamels, which, when put together (sometimes in microscopical fragments), and formed into a landscape, figures, or other design, are now called mosaics. The richer the colors and shadings, so as to produce fine pictures, the more striking the mosaics fall on the eye of MOSAIC AND PIETBA DURA. 427 the spectator. The Roman mosaics, in which prisms or threads of glass, of various sizes and shapes, compose the whole picture ; the Venetian mosaics, where the glass is a tessera or square shape, of some size, inlaid often in a cement base. The manufacture of true Roman mosaics has always been confined to the city whence its name is taken, and no country has entered into competition with Rome. They are composed of glass, sometimes called smalt, and some- times paste ; are made of all kinds of colors and every different hue. For large pictures they take the form of small cakes ; for small works they are produced in threads, varying in thickness from that of a piece of string to the finest cotton thread : large quantities of these, of all tints and colors, are prepared. A plate or slab of copper, marble, or slate is then provided, of the size and thickness required for the intended work. This slab is hollowed out so as to resemble the bottom of a box or a tray, to a depth propor- tioned to the work; this may vary from an inch to the eighth, or even the sixteenth of an inch, if the work is to be small. This hollow is then filled with plaster of Paris, well smoothed, on which the outline of the proposed design is very accurately traced, and an inked pen is passed over the outline to preserve it. Very few tools are required by the workmen, but for the large works, where comparatively large pieces are to be inserted, small shape-cutting ham- mers are made use of for splitting the cakes and reducing them to their proper size and form ; pincers also, of differ-" ent forms, are used for placing them equally. In very small works, instead of hammers, sharp-pointed pincers are made use of, like those with which diamonds are taken up, and sometimes a small tool like a scarpello. The heat of an oil lamp is required, to enable the workman to draw out the strips of glass to the desired fineness, even to that of 428 A POPULAR TREATISE ON GEMS. a hair. When this is all ready, the first operation is to dig or scoop out, with a scarpello of a proper size, a small piece of plaster of Paris from the bottom of the box or tray, without injuring the outline ; this is filled up with a kind of mastic or putty, like that which is used for panes of glass in the sashes of a window ; and the required piece of smalt or glass is then pressed into the composition. In this way, step by step, and from day to day, repeating the operation of scooping out a small piece of plaster of Paris, and never losing sight of the outlines, they gradually fill up the whole tray. In works of considerable dimensions, the workmen place the tray before them as painters place the canvas on which they are painting, and have the origi- nal always close to them. For smaller works they sit at a table, as if writing, and keep the work flat on the same. The designs used in these mosaics are for the most part copied from the pictures of some artist of eminence, the designers themselves being also a separate body, working for the mosaicisti, who mechanically fill up the spaces as above described. When the operation is completed, it is passed over a stone made perfectly smooth and cleaned of every kind of dirt ; it happens, however, that interstices, however minute, will be left more or less between the several small pieces of smalt inserted into the mastic ; these are to be carefully filled up with heated wax, applied with hot iron instruments from a pallet on which it has been prepared for the purpose, and much of the good effect and finish of the work will depend on the ability and care of the workmen by whom this operation is performed. A most remarkable specimen of this beautiful art was shown at the London Exhibition, by the Cavaliere Bar- bed ; it was a large round table, and represented cele- brated views in Italy; it was of singular delicacy and beauty of workmanship, the style of the design, the ex- MOSAIC AND PIETRA DURA. 429 quisite shading of the colors, the brilliant though softened effect of the group of views, the atmosphere and sky of each mingling into the same.ethereal tint, which relieved the eye and allowed it to rest with pleasure on the separate views : it was certainly a masterpiece. The author never left- the Crystal Palace without passing by the table, which always excited fresh admiration. There were two other mosaics, much larger than the former, and different in style, that were remarkably fine specimens of workmanship : one was a copy of a celebrated picture, by Guercino, a St. John the Baptist ; and the other a portrait of Pope Boniface the Second. A circular table, a square slab, and a picture represent- ing a view of PaBstum, were likewise among the Roman mosaics in the London Exhibition. Dr. Chilton, of New York, has a beautiful Roman mosaic of the Pantheon, about three inches long. In the New York Exhibition, in 1853, the large pic- ture of Pope Pio IX., in medallion size, was much ad- mired. In the Paris Exhibition, in 1855, many large works of Roman mosaics were exhibited ; one in particular, belong- ing to the Duke of Tuscany, required the constant work of fourteen years, and cost 700,000 francs. A large table in the rotunda of the panorama, of rich and elegant Roman mosaic, cost 400,000 francs. -^ The famous picture of the Campo-vacino, in Home, by Galand, cost the artist ten years' labor. Pietra dura, also called Florentine mosaic, consists in the manufacture of hard stone inlaid in a slab of marble ; they are, for the most part, of the quartz species, such as agates, jasper, chalcedony, carnelian, &c. ; also, lapis lazuli, malachite, and all such hard and colored minerals which, by their depth of color and brilliancy of lustre largely con- 430 A POPULAB TREATISE ON GEMS. tribute to produce a picture of a flower or a landscape, and all come under the name pietra dura of the Florentine school. In this kind of work, a slab of marble (generally black), of the required dimensions, and about one eighth to three sixteenths of an inch thick, is prepared, and the patterns to be inlaid are carefully cut out with a saw and file. The hard stones are worked into the required pattern by the ordinary methods of gem-cutting, and are accurately fitted into the spaces thus prepared, in a polished and finished state ; for if the whole were to be polished at once, some of the substances being softer than others, would be worn away too rapidly. The work, also, is liable to be spoiled by the accidental placing of one stone lower than another, and mistakes of this kind will often lead to the ruin of the whole. After the surface is thus prepared it is veneered on a thicker slab and is then fit for use. In point of diffi- culty of execution, durability, and taste, this process of inlaying in hard stones or gems may rank as the most im- portant purely decorative work within the whole range of mineral manufactures. In order to illustrate the peculiar mode of inserting the different pieces of agate, jasper, &c., in these beautiful works of art, and to' show also to those not familiar- with them the elegant and simple forms produced, we give the following diagram, showing a fac-simile of a portion of the inlaid-work in one of the tables which were exhibited in the London World's Exhibition, in 1851. In this diagram the dark line represents the outline of the flowers, leaves, &c., and the dotted part, the lines where the different pieces forming a single object are joined together. The extreme delicacy and accuracy of the joints can only be fully appreciated by the examination of the original specimens. MOSAIC AND PIETEA DUEA. 431 Fig. 11. True Florentine mosaic, of fine design and good taste, was in profusion from Tuscany and St. Petersburg. A jewel-case belonging to the Empress" of Russia, was particularly worthy of notice : it was constructed of wood, having the four sides and top covered with groups of fruit cut in pietra dura, in a style which may be called cameo- mosaic in rather high relief; the stones were so selected as to afford perfect fac-similes, in color, size, and even in in- ternal structure, of the fruit they represented, which were currants, pears, and plums, and the whole work was ex- quisitely finished. The King of Sweden sent to the London Exhibition, 432 A POPULAR TREATISE ON GEMS. an inlaid oblong table of granite, porphyry, and jasper, of beautiful workmanship ; the materials were the hard stones of Sweden, which being nearly of equal hardness, admitted of being polished after the work Was finished. An Indian chess-table with an inlaid border, and a num- ber of small objects from India, the ground being a white marble of a peculiar saccharoidal texture, attracted great attention. The pattern was a fine scroll-work, remarkable for the extraordinary delicacy and exactness of the stems of flowers and the perfect joints the stems were of flint. This and another Indian inlaid- work are said to be of great antiquity. No comparison can be instituted between these Indian and 'European works, the mechanical execution of the former being at least equal to the best of those which have rendered Florence so justly celebrated, while the taste and design exhibited in them are greatly superior to inlaid work in marble. The great expense of inlaying hard- pebbles, which can only be cut as gems, and the excellent effect that may be produced by imitations in which marble of various kinds, shells, cement, and glass, replace the jasper and agate of Florentine mosaic, have caused the introduction into Eng- land, and elsewhere, of a manufacture which may be called inlaid marble work. In Derbyshire this branch of manu- facture has become very important. There are two prin- cipal methods of producing marble mosaic ; that followed in Derbyshire, where a recess is chiselled out of a solid block of marble, serving as the ground ; and that pursued in Devonshire, where the whole surface is in fact veneered; numerous marbles of various colors and forms being merely cemented together on a base, which may consist of slate, or any kind of marble; the whole surface being after- wards polished together. In Malta the former process is followed, while in Russia the malachite inlaid work is per- MOSAIC AND PIETRA DURA. 433 formed, as just described. The Duke of Devonshire loaned his fine collection of Florentine mosaics to the manufac- turers, from, which they copied the butterflies, leaves, and sprigs of jessamine, for which these mosaics are so cele- brated. These works being used as guides, the art of in- laying was brought into successful operation, and materials foreign to the vicinity, as malachite from Russia, Conti- nental marbles, Avanturine and other glasses, from Venice, with some cements, have been introduced into them. The manufacturers at Matlock, Ashford, Bakewell, Buxton, Derby, and Castleton are all doing a thriving business. A table with a wreath of flowers of extremely compli- cated pattern, and admirably finished, with a vast number of detached marbles, of Derbyshire work, owned by Mr. Yallance, attracted general attention at the "London Exhi- bition. Although not to be compared with the Florentine work, there were, nevertheless, much skill and labor be- stowed upon it. A number of other tables of inlaid work, of the cinque- cento style, were likewise weh 1 executed. The exhibition of Derbyshire inlaid work was very large. A mosaic chess-table from the Isle of Man ; from Lisbon, interesting specimens of mosaic, composed of sixty speci- mens of Portuguese marbles ; and from the Cape of Good Hope, a peculiar kind of inlaid marble work, were at the London Exhibition, and all more or less interesting. Clay and Porcelain Mosaics* The encaustic and mosaic tiles used by the ancients for ornamenting houses, for pavements and walls, have of late years been extremely well imitated, both in England and the United States. The encaustic or inlaid tiles are made by pressing clay in in 434 A POPULAR TREATISE ON GEMS. the plastic state into an embossed plaster mould, the pattern or design on the mould being raised. When the tile is withdrawn from the mould, the outline of the pattern is indented, and the indented parts are filled in with colored liquid clays, according to the colors it is desirable to pro- duce. The surface is then scraped quite flat, until the pat- tern appears well defined. The tile is then heated, or as it is termed, fired, which brings out the colors to the proper tint. The Venetian tiles and mosaics are produced by the com pression of powdered clays into metal dies, of any geometri- cal form that may be devised, the clays having been previ- ously stained with metallic colors. - Each tile or tessera is, of course, of the same color throughout. When fired, they are arranged on a smooth platform, with the faces downward, according to the design intended, after which liquid Roman or Portland cement is poured upon them, and they are thus formed into slabs of any size required. The Alhambra or Spanish tiles are made by pressing plastic clays into an embossed mould, which forms grooves or indentations ; these tiles are then fired, and come out of the oven with the pattern formed. The indentations are then filled in with enamels of various colors and fired again, which produces a brilliant efiect, and renders the tiles suit- able either for floors or the interior walls of buildings. A mosaic pavement, composed of tesserce of vitrified clay, of several colors and shapes, all produced by machinery with great rapidity, and without the necessity of chipping any of the tesserce, and at the same time making an endless variety of patterns, is produced in England, in the follow- ing manner : The clay being prepared in the usual way, by washing and sifting, and stained with various metallic oxides (oxide cobalt, blue smalts, manganese, zaffre, red lead, crocus mart-is, an rum musivum, oxide chrome, copper MOSAIC AND PIETEA DTJBA. 435 scales, &c., the principal ingredients used), is formed into thin ribbons, about three eighths of an inch thick and from three to four feet long, by a machine ; out of these ribbons the tessercB are cut by a patented machine, with great ra- pidity, and when dry are baked in saggers in the usual way. Pavement slabs are made by laying these tesserae face downwards on a perfectly flat slate, the pattern, of course, being reversed, and covering their backs with a layer of Portland cement, and two layers of rough thin tiles, care- fully embedded in the cement. In this way strong slabs are formed, of from an inch and three quarters to two inches thick, which are almost perfectly impervious to moisture or rising damp. The capitol extension, in the City of Washington, United States, is embellished with encaustic tiles ; and both the pavement in the halls of the house of representatives and senate chamber, and the avenues leading to them, and the encased walls, are laid out with bright-colored tiles, in the most gorgeous manner. Mosaic Tiles made with Soluble Glass. The many useful applications of soluble glass (which may be the silicate of soda, or the silicate of potash, or both alkalies combined with the silica), form a new era in the production of an artificial stone, which, if properly adapted, must ultimately supersede all other artificial stones or cements of any kind. If grains of sand, pebbles, lime, marble, or even granite, clay, and fluor-spar, are mixed with soluble glass into a paste of the consistency of putty, and this paste is then moulded into any required form, after slowly air-drying and burning the articles thus manufactured in a kiln at a bright-red heat, which may be 436 A POPULAR TREATISE ON GEMS. maintained for any length of time, by which process the alkali contained in the soluble glass is set free, the silica combines with the lime, and more particularly with the fluor-spar (fluoride of calcium), so durable a cement is formed thereby, that it will not admit of the smallest absorption of moisture, and consequently is absolutely un- attackable by frost. By applying the chloride of calcium in solution to the cement, the supposed objection that the salts of soda, or alkali, are efflorescing by degrees, is hereby obviated, for the chloride of calcium at once absorbs the alkali. Soluble glass may be colored by various metallic oxides, so as to produce, when heated, very sharp colors, similar to enamels, and may also be employed for a coating over other paints, such as fresco, &c. As a cement for joining together heterogeneous and ho- mogeneous substances, it is unsurpassed, and when applied, renders the substances so coated both water and fire proof. If soluble glass is intended for a varnish, the proper spe- cific gravity is 1'165, but for a paint it may be reduced to that of water. In France, soluble glass is much used in coating com- mon building-stones, for the purpose of rendering them damp-proof. Marble buildings and damp cellars may be made impervious to dampness by varnishing the surface with soluble glass ; although the proper mode is to exhaust the air from the stone or brick, and then impregnate, it with soluble glass by pressure. A patent was lately taken out in England, for preserving building, pier, and wharf stones, by first coating them with a wash of chloride of cal- cium, and afterwards by the application of the concentrated solution of soluble glass, repeating the operation several times. Soluble glass was introduced into the United States, by the author of this work, in the year 1831, under MOSAIC AND PIETEA DURA. 43} the authority of the government, for the purpose of pro- tecting the cannon and balls, exposed to the weather in the Brooklyn Navy Yard, against rust ; for this purpose, when treated with the various coloring pigments, such as oxide of manganese, umber, terra di sienna, ochre, Venetian red, ultramarine, &c., it is admirably adapted. Q Diamond Oriental OK "/: Or. Topaz, -ItnetfiYst Jlnbv Ckrvsoberfl Chrsobtil a a - tiarnet ~~ - Cinnninfini C 1[H ' Blood -Jaspe Chciti-edonv (Itrxopnise ftridffte Chwsolite Opal 1 tus(. Lapis stoiie Lazuli TuriputHSf Malachite Amber mrnam tmwm i IgM , 1 HHHI />A.-,,y,x, /, dTO ^c Ltpidatitv .Varityan Serpentine Hoc/use Labnada Vurblt Granite Porphrrr a E EXPLANATION OF PLATES. PLATE II. THE MOST REMAKKABLE EOTJGH DIAMONDS. No. 1. The Nizam, from India; it weighs 340 carats, is valued at five millions of francs, and belongs to the King of Golconda. No. 2. The great rough Diamond, as described by Tavernier, from India, weighing 282 carats. No. 3. The great South Star, from Brazil, weight when rough 254i carats, was found in the mines of Begagem, in the province of Minas Geraes, in Brazil. It is as clear as water, slightly tinged with yellow ; it is valued at two and a half millions of francs ; it is thirty millimetres in height, forty in length, and twenty-seven in breadth. Its shape is a twelve-faced rhomboid, presenting altogether twenty-four triangles. DIAMOND LATHE. PL.2. -<^ ^. fTfFjn PL. 3 THE. LARGE ROUGH DIAMONDS. PLATE III. KEMABXABLE BOUGH DIAMONDS. No. 4. The great Spheroidal, six-sided, with forty-eight facets. " 5. The spheroidal Diamond, with twenty-four facets. " 6. A dodecahedral-pentagonal rough Diamond. " V. A dodecahedral-rhomboidal rough Diamond. " 8. An Octahedron, with twenty-four facets. " 9. An Octahedron, the primary form. PLATE IY. REMAKKABLE BOUGH DIAMONDS. 0i 10. A rough Brazilian Diamond. " 12. A regular Tetrahedron. " 12. A round, concretional, rough Diamond, called Boort, " 13. A rough Brazilian Diamond. " 14. A rough cubical Diamond. " 15. A rough Brazilian Diamond. " 16. A truncated octahedron Diamond. 17. A rough Diamond, described by Ta vernier. " is. A triangular crystal of Brazilian Diamond. " 19. An Octahedron, with modified secondary form. PL. 4 ROUOH O/ AM ON OS IUIIFBESI ROUGH DIAMONDS PL. 6. PLATE Y. No. 1. The improved Diamond Lathe (exhibited in the Paris Exhibition, 1855, by Phillippe). No. 2 and 2 a. The pincers, front and side view. THE PBINCIPLE OF CUTTING. No. 3. a. The table of a brilliant. &. The triangular faces. c. The angles terminating into planes, d. Lozenges 4 large and 4 small, e. The planes on the edge of the stone. No. 3 a.f. The angles parallel with the planes, g. Pavilion or facets corresponding to Lozenges.* h. The collet of the bril- liant. No. 4. A rough Diamond, cleansed. " 5. Cut of the crown. " 5 a. The three different cuts. a. The table. 5. The girdle. c. The collet. No. 6. A Brilliant not recut. " 7. A Brilliant recut. 8. Hose Diamond, a. The crown. 5. The facets. * Lozenge is the geometrical form of a rhomb. PLATE VI. THE MOST CELEBRATED OUT DIAMONDS. No. 1. The Grand Mogul; it weighs 279 carats, and is valued at twelve millions of francs. No. 2. The Orlow, the great Russian Diamond, weighs 195 carats, and is the size of a pigeon's egg : cost two millions of francs and a pension of one hundred thousand francs.* No. 3. The table Diamond of Ta vernier, weighing 242 carats. " 4. The Polar Star, weighing 40 carats. " 5. The Shah, belonging to the Russian crown, weighing 95 carats. * It is on the top of the Russian sceptre, and has the form of a knob of a cane ; the under surface is a plane. THE MOST CELEBRATED CUT DIAMONDS . PL. 6. %> tnn B PL.T. THE. MOST CELEBRATED CUT DIAMONDS 6 7 PLATE VII. THE OELKBEATED OUT DIAMONDS. No. 6. The Nassack, weighs 78| carats; was sold, in 1839, foi seven thousand six hundred pounds sterling, to the Marquis ol Westminster. No. 7. The great India half-cut Diamond, weighing 112 carats. No. 8. A brillianted Rose in pear-shape, from India, weighing 16 carats. No. 9. Another Rose in pear-shape, weighing 94^ carats. No. 10. A recut India Brilliant, weighing 29 carats. No. 11 and 11 a. The South Star of Halphen, weighing 124 carats. No. 12 and 12 a. The Regent, or Pitt ; it weighs 136 carats, belongs to the French crown, is valued at five millions of francs, and is certainly the best-proportioned Diamond in the world ; it is perfectly pure and transparent, and sparkles with a magnificent play of color. PLATE Till. THB CELEBRATED OUT DIAMONDS. No. 13. The Piggot, belonging to England, weighs 82 carats. No. 14. The Pacha of Egypt's Diamond, weighs 49 carats. No. 15. The Koh-i-noor, as it came from India ; and 15 a, its present form, from a side view. No. 16. An India pear-shaped Brilliant, weighing 31 1 carats. No. 17. A Half-Brilliant, faceted, weighing 14J carats. N"o. 18. Large Rose Diamond, of 280 carats. No. 19. An irregular Rose Piamond, in pear form, weighing 20 carats. No. 20, An India Brilliant, described by Tavernier, weighing 52 carats. No. 21 and 21 a. Large table Diamonds, step-cut. THE. MOST CELEBRATED CUT DIAMONDS. PL. 8. ^ ; THE. MOST CELEBRATED CUT DIAMONDS . 22 PL. 9. PLATE IX. THE OELEBBATED OUT DIAMONDS. No. 22. The great Austrian Brilliant, belonging to the Grand Duke of Tuscany, weighing 139 carats ; valued at seven millions of dollars. No. 23. The Eugenie Diamond, belonging to the Empress ol France, weighing 51 carats. No. 24. The Hope Diamond, a beautiful blue Diamond, weigh- ing 44i carats. No. 25. A Brillolet of 16 carats. No. 26. A knob-shape of 10 carats. No. 27. A table-shape of 10 carats. No. 28. A flat Diamond of 20 carats. No. 29. A flat Diamond of 14 carats. No. 30 and 30 a. The celebrated Sancy, belonging to the French crown-jewels, weighing 33 carats, of pear-shape ; is valued at one million francs. No. 31. A large cleaved Diamond, of 64 carats, from India. PLATE X. Ko. 1. Rock-Crystal Group, from Arkansas, IT. S. Size and weight of Diamonds, both round and square, from that of half a carat to 18^ carats. PL.X. PL.X/. PLATE XI. AMEBICAN No. 1. California Marble. u 2. Verde Antique, from Vermont. 3. Shell Marble, from New York. " 4. Tennessee Marble. " 5. Bale's Breccia Marble, from Lancaster, Pa. " 6. Potomac Marble. " 7. Variegated Marble, from the State of New York. PLATE XII. No. 1. Black Marble, with petrified volutes (Pyramidella tur Unella). No. 2. Red, green, and white brecciated Marble, from Sicily. No. 3. Red mottled Marble, tertiary fresh-water Limestone, from Swabian Alps, cut parallel to the planes of the layers. No. 4. Pale, yellow, and violet Marble, from the Jura, in Wiirtemberg. No. 5. Reddish-yellow and bluish-red mottled Marble, from Wiirtemberg. No. 6. Marble, tertiary, cut perpendicularly to the planes oi the layers, from the Alps. No. 7. Pale-yellow Marble, and violet Flakes, from Wiirtem berg. PL.XI/. PLJfM. PLATE XIII. No. 1. Tertiary brecciated Marble, from the Pyrenees. No. 2. Red Granite, consisting of red felspar, grey quartz, anc black mica, from Upper Egypt ; used by the ancient Egyptians ir their monuments. No. 3. Fibrous Calcite, or so-called Thermal Tufa, Sprude 1 stein, from Carlsbad. No. 4. Compact Brown-spar, from Gibraltar. No. 6. Agate Marble, from Algiers. PLATE XIY. No. 1. Kyanite, light-blue and oblique rhombic prism, with truncation, from St. Gothard. No. 2. Amphibole or dark-green Hornblende, Actinolite, an oblique rhombic prism, from Tyrol. No. 3. Precious Serpentine, in right rectangular prisms, from Norway. No. 4. Lumachelli or Fire Marble, containing fossil shells; the variegated colors are owing to nautilus or ammonite, from Corinthia. No. 5. Ruin Marble, cut perpendicularly to the planes of the layers, from Tuscany. -$o, g. Pea-stone, calcareous Stalactite, from the hot springs of Carlsbad. No. 7. Dark-brown ribbon Agate, Arabian Onyx, from the East Indies. No. 8. Pale-yellow Marble, from Florence. No. 9. Variegated Marble, containing Corals, from the transi- tion rocks of Nassau. No. 10. Bed brecciated Marble, from Italy. No. 11. Black Porphyry, from Sweden. PLJ(/V. PL. XV. PLATE XY. No. 1. Egyptian Jasper. No. 2. Ribbon Jasper, striated with red and green, froir Siberia. No. 3. Pudding-stone or Quartz Conglomerate, from Scotland. No. 4. Horny-colored Agate, from the East Indies. No. 5. Chrysolite, from the East Indies. No. 6. Noble Garnet, Pyrope, from Bohemia. No. 7. Dark-yellow Topaz, burnt, and called Balais, from Brazil. No. 8. Granite, from Milan. No. 9. Wood Opal, a petrified pine, from Hungary. No. 10. Black ribbon Agate, from the East Indies. No. 11. Green Tourmaline (Brazilian Emerald) in Dolomite, from St. Gothard. No. 12. Moss Agate or Mocca-stone, from the East Indies. No. 13. Dark Topaz, from Brazil. PLATE XVI. No. 1. Black and white mottled Marble, from the monotniE limestone of Ardennes. No. 2. Red antique Porphyry, from Upper Egypt. No. 3. Blue Copper, Azurite, from Germany. No. 4. Malachite, Green Copper, from Siberia. No. 5. Natrolite on Clinkstone, from Bavaria. No. 6. Clear-yellow Amber, inclosing several flies, from the coast of the Baltic, near Dantzic. PL.W. PLXVII. PLATE XVII. No. 1. Dark-green Serpentine, from the Apennines. No. 2. Amazon-stone or apple-green Felspar, an obliqne rhom bic prism, from the Ural Mountains. No. 3. Fortification Agate, from Oberstein. No. 4. Green Porphyry Felspar, from Greece. No. 5. Serpentine, Ophicalite, or Verde de Corsica duro, from Corsica. No. 6. Labrador Felspar, from Labrador. 458 INDEX. Borax, double refraction of, 88; reagent, 116. Botryoidal, 72. Brachydiagonal, 46. Brachydomes, 47. Brachypyramids, 47. Brazil, discovery of diamonds in, 1ST; revenue from diamonds in, 201. Brewsterline, 265. Brilliant, the, 161. Brillionets, 161. Bromine, 119. Bronzite, fusibility of, 116. Brown spar, 56. Burning of gems, 171. 0. Cabochon cut, 165. Cachelong, an opal, 807. Cadmium, test of; 125. Cairngourm crystals, 261. Calamine, 55. Calc spar, 43, 65, 66, 70, 73 ; hardness, 78 ; double refraction, 86; varieties of, 364. Calcareous scheelite, refraction of, 88. Cameos, shell, 425. Cannel coal, described, 354. Carat, origin of the word, 181 ; weight of four grains, ib. Carbon, 120. Carbonate of soda, reagent, 116; refraction of carbonates, 87; electricity, 99. Carbuncle (see Spinelle), 228 ; garnet, 251. Carengeair's goniometer, 5S. Cornelian, hardness of, 80; described, 279. CatVeye quartz, described, 270. Caves, list of American, 880. Cerium, test of, 127. Chabasite, 56, 65. Chalcedony, 73; hardness of, SO; refrac- tion of, 88 ; described, 277. Varieties 1, Chalcedonyx; 2, Mochastones; 3, Kain- bow : 4, Cloudy ; 5, Plasma ; 6, Semicar- nelian or ceregat ; 7, Sappharine ; 8, St Stephen's stones, 278; varieties of, 77. Chalcopyrite, 64. Chalk, 365. Chemical properties of minerals, 102 ; reac- tion, 113. Chlorine, 119. Chlorophane (a fluor spar), 335. Chromate of lead, refraction of, 87. Chromium, test of, 127. Chrysoberyl, degree of hardness, 80 ; real gem, 136; same as cyinophane, 225. Chrysolite (Peridote, olivin), nardness ot, 80 ; real gem, 136 ; oriental, a sapphire, 216; refraction of, 87; Ceylon, a tourma- line, 256; described, 294. Chrysoprase, described, 292 ; value, 294. Cinnabar, refraction of, 88. innamon stone or Essonite, 253 ; see Hya- cinth de Ceylon. Cleaning gems, 172. Cleavage, varieties of; 76. Clinopinacoids, 51. Clinoprisms, 51. Clinopyramids, 51. Coal, 354 ; American coal-fields, ib. Cobalt, solution of, reagent, 117; test of, 125. Cobaltine, 80, 31. Collet the, explained, 161. Colophonite, a garnet, 249. Color, change of, 93; table of colors of minerals, 96 ; of gems, 136. Combinations, 81. Conazeranite (felspar), 314. Copper, test of, 126. Coral, described, 419 ; varieties of red, 422. Cordierite, a real gem, 136. Corundum, hardness, 78 ; refraction of, 87 ; description of, 214; see Sapphire. Corundum, common, or Diamond spar, de- scribed, 223 ; granular, or emery, 224. Crown-jewels of France, value of; 207. Crown-jewels of Queen Victoria, 210. Cryptoiine, 265. Cryptocrystalline minerals, 73. Crystalline, 19. Crystallized, 19. Crystals, defined, 20 ; described, &. ; sys- tems of, ib. ; imperfections of, 54 ; strise 55 ; drusy, 56 ; measurement, 58 ; macles or tw4n crystals, 61 ; irregular aggrega- tion, 70. Cyanite, 73 ; described, 827. Cymophane (oriental chrysolites), refrac- tion of, 87 ; see Chrysoberyl. D. Deltoid dodecahedrons, 28; sign, 80. Derivation of forms, 27. Diamond, 24, 25, 29; hardness of, 78, 80 i double refraction of, 87 ; first cut by Ca- radossa, 151 ; manner of cutting, 156, 183 ; polishing, 158 ; forms of, 161 ; discovery in a diamond lens, 182 ; general account of, 183, etc. ; pure carbon, 184; artificial, ib. ; form of crystals, 185 ; color, ib. ; the INDEX. 459 compact, ib. ; the original bed of, 187: loss In cutting, 193; Hindoo division of. 195; value, Vt. ; color, purity, ib.; de- gree of clearness, ib. ; cat and size, 196; prices of, 197-8; celebrated diamonds, 154, 193, 203 ; the largest known, 208 ; in Victoria's crown, 211 ; at the Industrial Exhibition, 212. Diamond grinders, 155. Dimorphism, 110. Dioptase, double refraction of, 88. Disthene (Kyanite, sappare), described, 321. Ditetragonal, pyramids, 36. Divelsteene, 156. Dodecahedrons, subdivided, 22. Dolomite, double refraction of, 87. Double facet cut, 165. Doublets, 180. Druses, 71. Drusy crystals, 56. Dyakisdodecahedron, 30; sign, 31. E. Edingtonate, double refraction of, SS. Electricity of minerals, 99. Electro-chemical elements, table of, 105. Electroscopes, 99. Elongated brilliant facet cut, 165. Emerald, hardness of, 80; double refrac- tion, 85; a real gem, 136; the oriental, a sapphire, 216; described, 235; emerald proper, ib.; how cut, 237; value, ib.; remarkable emeralds, 238 ; the Duke of Devonshire's, 239 ; the Brazilian, a tour- maline, 256. Emery, a common corundum, 224. Engraving on gems, 167. Essonite, or cinnamon-stone ; hardness of, 80; real gem, 136, 250; described, 253. Euclase, double refraction of, 87; descrip- tion of, 234. F. Facets, 161. .Fablore, 63. Felspar, 52, 53, 75; described, 312; com- mon, 315; ad ul aria. 312; march isonite. 814; leclite or helleniaU, conazeranite. ib.; amazon-stone, 315; porphyry, 391 ; sienete, 893. Fish-eye (adularia), 31i Fluor spar, crystalline forms, 23 24, 25, 56, 63, 65, '70; hardness, 78, 80; ciouble re- fraction of, 88; electricity, 99; describ- ed, 333. Fluorine, test for, 120. Foil, use of, 169. Form, primary, 26 ; semi-tesseral, 28 ; par- allel semi-tesseral, 30. Forms of crystalline aggregates, 71. Fortification agate, 284. Fracture surfaces, 78. Fusibility, test minerals as to, 115. G. Galena, 23, 24, 56, 63. Garlic, used in repairing gems, 170. Garnet, 23, 25, 27 ; hardness of, 80 ; double refraction of, 88 ; magnetic, 100 ; a real gem, 136 ; described, 247 ; varieties, 24S ; Syrian, Bohemian, Ceylonian, Aplome, ib.; precious or almandine, 24S ; coloph- onite, 249; allochroite, ib.; grossular, 250; topazolite, ib.; melanite, pyrena- ite, ouwarowite, ib.; the ancient car- buncle, 251. Gems, 135; enumerated, 136; color, grav- ity, and hardness of, ib.; chemical char- acter, 139; composition, ib.; artificial production, 140 ; geological character, 145; geographical distribution, 140; di- vision and nomenclature, 147; history of, 148; superstitions as to, 149; sculp- ture in, 151 ; grinding, 153 ; engraving, 167; sawing and drilling, 168 ; polishing materials, ib.; heightening color of, 169 ; setting, 171; cleaning of, 172; imita- tions,^.; 1, pastes, ib.; 2, doublets, ISO ; 3, burning, 180; price of, 181; optical use of, 181. Girasol sapphire, 216 ; fire opal, 304 ; adu- laria, 313. Girdle, in diamonds, what? 161. Glucina, test of, 123. Goldstone, a paste, 278. Goniometers, 58. Goutte de sang, a spinelle, 228. Grand mogul diamond, 193, 203. Granite, described, 896; American varie- ties, 397. Gray copper ore, 28, 68. Grossular garnet, 250. Gypsum crystals, 51, 56, 68, 74; doable refraction of, 88 ; tntin gypsum, 341 ; al- abaster, ib. 460 INDEX H. Haematite, 65. Hardness of minerals, 78 ; Mob's, scale of, ib.; rough scale, 79 ; of precious stones, 80 ; of gems, 136. Hatchet-stone (jade), 361. Hausmanite, 64. Hauyne, described, 822. Heliotrope, described, 282. Hellefliata, or Leclite (felspar), 314. Helvine, 28. Hemihedric crystal, 21. Hetnimorphism, 54. Hemiorthotype system, 21. Hexagonal system, 21, 39; pyramids 40; dihexagonal, 41 ; rbombohedral, 42. Hexahedron, 22, 23 ; sign of, 27. Hexakisoctahedrons, 25 ; sign of, 27. Hexakistetrahedron, 28; sign, 30. Holland diamond, 206. Holobedric crystals, 21, 22. Hope diamond. 206. Hornblende, 68, 320. Hornstone, described, 277. Hyacinth, hardness of, 80; oriental, a sap- phire, 215; a variety of zircon, 246 ; de- scribed, 247. Hyacinth de Ceylon (Essonite, or cinna- inon-stone), 258. Hyaline, 19. Hydrate of magnesia, double refraction of, 88. Hydrometer, 81. Hydrophane, a variety of opal, 305 ; curi- ous property, ib. Hydroxide of iron, double refraction of, 88. Hypersthene, not hornblende, 820; de- scribed, ib. I. Iceland spar, 66 ; double refraction of, 86 ; described,. 364 Icositetrahedrons, 22, 24 ; sign of, 27. Idocraso, double refraction of, 88 ; describ- ed, 321. Ignoble metals, 101. Imitations of gems, 172. Indicolite (Brazilian sapphire), 256. Iodine, test for, 119. lolite, real gem, 136; described, 297; di- chroite; peliom, lynx and water sapphire, 298. Iridescence, 93. Iron, double refraction of, 88; test olj 127. Iron pyrites, 30, 81, 55, 68. Irregular aggregation, 70. Isomorphic substances, 111. Isomorphism, 110. Itacolumite, diamond-bearing rock, 188. J. Jade (nephrite, hatchet-stone, punamu), described, 361. Jargon (see Zircon), 244 ; described, 246. Jaspachates, a variety of agate, 284 Jasper described, 273 ; varieties : 1, Egyp- tian ; 2, Ribbon spar, 276 ; jasper opal, 308. Jet, hardness of, 80 ; described, 353 ; a bi- tuminous coal, ib. Jewish tribes, gems allotted to, 149. Jeweller's wax, 172. K. Kaolin, 75. Kneeshaped crystal, 64. Kohinoor, a celebrated diamond, 154; its loss in cutting, 193 ; history of, 208. Kuinur, a celebrated diamond, 154. Kyanite (sappare, disthene) described, 827. L. Labradorite, 70 ; not felspar, 317. Lamellar, 71. Lapidaries, ancient, 151; s6ciety of, 153; gem lapidary, 163; common, 164; his apparatus, ib. Lapis lazuli, or Armenian stone, described, 322 ; uses of, 323. Lava described, 360. Lava, black glass lava, or obsidian, 310. Lazulite, hardness of, 80 ; azure-stone, 324 ; used to imitate lapis lazuli, ib. , 66 ; test of, 125. Leclite (felspar), 314. Lepidolite, described, 339. Leucite, 27. Lievrite, 48. Lithia, test of, 121. Lime, test of, 122. Lithographic stone, 366. Love's arrows, a rock crystal, 261. Lustre, 93 ; degrees of, 94 ; varieties of, ib Lyncurium, not tourmaline, 258. IND EX. 461 M. Macles or twin crystals, 61. Macrodiagonal, 46. Macrodoines, 48. Macropinacoid, 48. Macroprisms, 48. Magnetic iron ore, 24, 63. Malachite, 74; hardness of, 80; describ- ed, 835; beautiful articles made of, 338. Manganese, test of, 125. Marble (Carbonate of lime), described, 264; best localities, 366 ; ancient marbles, 367 : French, ib. ; English, 863; varieties of Derbyshire, ib. ; marble statuary, 370, 876 ; American marbles, 871, 8S3 ; white, ib. ; ancrinital or bird's-eye, 372 ; mar- bles, &c., in N. Y. Geological cabinet, 373 ; breccia, 375 ; serpentine or verd an- tique, ib. ; leocadia breccia, 876 ; Egyp- tian, 382; Italian, ib. ; shell marble, 885. Marcasite, 66 ; or pyrites, 390. Marekanite, brown obsidian, 310. Measurement of crystals, 58. Meerschaum, described, 857; uses of, 358. Meionite, double refraction of, 888. Melanite, garnet, 250. Mellite, double refraction of, 88. Mercury, test of, 124 Mica, double refraction of, 88 ; described, 889. ' Microcosmic salt, reagent, 116. Mineralogy, how limited in this work, 16. Minerals, forms of, 19 ; crystalline, amor- phous, ib. ; physical properties, 75 ; hard- ness and tenacity, 73 ; specific gravity of, SO; optical properties, 84; double re- fraction, 85; polarization of light, 89; pleochroism, 92 ; iridescence, 93 ; lustre, ib.; color, 95; phosphorescence, 98; magnetism, 100 ; smell, taste, touch, 101 ; chemical properties, 102; composition, ib. ; influence of chemical composition on external character, 109; chemical re- action, 113; fusibility, 114-; solubility, 11T; classification, 129 ; orders of, 134 Mispickel, 66. Mix facet cut, 164 Mocha stones, chalcedony, 278. Mobs; his system of crystallization, 21; scale of hardness, 73. Molybdite, double refraction of, 88. Monoclinochedric system, 21, 49 ; its forae, 49; combinations, 51. Months, gems, allotted to, 149. Moonstone (Adularia), 318. * Moroxite, an oolite, 387. Mosaic, 426; Roman, 427; Florentine or pietra dura, 429; clay and porcelain, 433. Murchisonite (felspar), 314' Nassak diamond, 198; its value, 200, 204, 210. Natrolite, fusibility of, 115; described, 332. Naumann, his system of crystallization, 21. Nepheline, double refraction of, 88. Nephrite or jade, 361. Nicholson's hydrometer, 81. Nickel, magnetism of, 100; test of, 125. Nitric acid, test, 119. Nizam diamond, 208. Noble metals, 108. Non-metallic elements, 113. o. Obsidian, hardness of, 80; described, 809. Octahedron, 23; primary form, 26; how distinguished, ib. Ofigoclase, 69. Olivin, or Chrysolite, 294 Ouwarowite, garnet, 250. Onyx, carnelian, 280 ; agate, 288 ; describ- ed, ib. ; cameos of, ib. Oolite, a calcareous spar, 365, 836. Oolitic crystals, 78. Opal, 73 ; hardness, 80 ; double refraction, 88 ; iridescence, 93 ; described, 299 ; pre- cious opal, ib. ; mother of opal, 801 ; cel- ebrated specimens, 802; fire opal, or girasol, 304 ; common opal, 805 ; hydro- phanes, ib. ; semi-opal, 806 ; wood opal, ib. ; cachelong, 807 ; Jasper opal, 808 ; Ceylon or water opal, ib. Orders of minerals, 137. Oriental and occidental gems, 147. .' <^ Orlow diamonds, 203. Orthopyramids, 51. Orthoprisms, 51. Orthopinacoids, 51. Orthotype system, 21. Orthoclase, 52, 68; fusibility, 115. Oxahverite, double refraction of, 88. Oxide of tin, double refraction of; 88, Oxidized stones, 134 Oxidized ores, 134 462 I N DEX. P. Pastes and artificial gems, 172 ; receipts fo colored, 176 ; how detected, 179. Paunched diamonds, 195. Pavilion facets, 162, 164 Pearls described, 400; how formed, ib. localities, 401; value of, 407; Unite States pearls, 409 ; artificial, 415. Peliom, a variety of iolite, 298. Pentagonal dodecahedron, 30; sign, ib. Pentagonal dodecahedron, and pentagona icositetrahedron, not observed in nature . 81. Peridote (see Sapphire, Chrysolite),216, 294 Phosphates of lead and lime, double re fraction of, 88. Phosphate of lime, 388 ; its uses, ib. Phosphorescence, 98. Phosphoric acid, test of, 118. Phosphorite, 388. Pietra dura (Florentine mosaic), 429. Piggot diamond, 206. Pisolite (calcareous spar), 365, 386. Plasma, chalcedony, 278. Plaster of Paris ; a gypsum, 342; constitu- ents, ib. Platinum, test of, 126. Pleochroism, 92. Point diamonds, 161. Polar-star diamond, 206. Polarization of light, 89; instrument for observing, 90. Porodine, 19. Porphyry, a compact felspar, 391 ; Ameri- can varieties, 392. Potassa, test of, 121. Prase, common quartz, described, 271. Prehnite, 56. Prismatic topaz, hardness, 78. Pseudomorphism, 74. Punamu (jade), 361. Pyramidal system, 21. Pyrenaite, garnet, 250. Pyrites described, 390; also called Marca- site, ib. Pyrope, a garnet, 248. Q. Quartz cpmmon, Eose quartz, cats-eye, prase, avantnrine, 269. Quartz crystals, 55, 56; hardness, 78 ; double refraction of, 87, 88 ; an oxidized stone, 184; a gem^ 136 ; described, 259. Queen Victoria's crown, 210. R. Rainbow chalcedony, 278. Bed silver, double refraction, 88. Eefraction, double, 85 ; table of, 87. Eegent diamond, 154, 193, 204. Eeniform crystals, 72. Ehombic system, 21, 45. Ehombic dodecahedron, 23 ; sign of, 27. Ebombohedral system, 21. Ehombohedron, 42 ; combinations, 44. Eibbon spar, 276. Eock of Gibraltar, carbonate of lime, 386 Eock crystal, 78; hardness of, 80; de- scribed, 260; varieties, 261; specimens, 262; water in them, 265. Eock salt, hardness, 78; double refrac- tion, 88. Rose diamond, 162. Rose manganese, described, 391. Rose quartz, 269. Eubellite, double refraction, 88; a real gem, 136 ; tourmaline, 255. Euby, hardness of, 80 ; a variety of sap- phire, 214, 215. Juby cat's-eye, 216. Euby spinelle, almandine, balais, varie- ties of spinelle, 227, 228. lussia, discovery of diamonds in, 189. ~^util, double refraction of, 88. s. Saline ores, 134. aline stones, 134. ancy diamond, 204 ; history of, ib. iappare (kyanite, disthene), described, 327. appharine, a chalcedony, 278. sapphire, hardness of, 80 ; iridescence of, 93 ; real gem, 136 ; synonymous with corundum, 214 ; description of, ib.; va- rieties, 215; ruby, oriental hyacinth, amethyst, sapphire, and topaz, 215; aquamarine, chrysolite, and emerald, 216; its constituents, 216; locality, 217; mode of cutting, ib.; uses, 219 ; value, ib. ; remarkable sapphires, 221, 222 ; Brazilian sapphire or indicolite, a tour- maline, 256 ; lynx and water sapphire, iolites, 298. arda, ancient name for Carnelian, 279. ardonyx, a carnelian, 280; agate, 289' cameos and intaglios, 290. atin gypsum, described, 341. atin spar, described, 340. calenohedron, 43. INDEX. 463 Scapolite, 79. Schlaggenwald fluor spar, 70. Schorl, electric, a tourmaline, 256; origin of the name, 258. Sculptors in gems, 152. Selenium, test for, 118. Semi-camel ian, 278 ; a chalcedony, 1b. Semi-tesseral forms, 28. Serpentine, described, 362. Setting of gems, 171. Shah diamond, 206. Shrugging in diamonds, 195. Siberite, a tourmaline, 255. Siderite, 56. Sienite (felspar and hornblende), 893; American varieties, 894. Signs, crystallographic, 27. Silver, test of, 126. Soda, test of, 121. Solubility, .17 Soluble glass, 435. Somerviilite, double retraction of, 88. South star diamond, 193, 210. Specific gravity of minerals, 80 ; how as- certained, ib,; of gems, 136. Spinel, spinelle, 23, 63; hardness, 80; double refraction, 87; real gem, 136; described, 227; constituents, ib.; varie ties, 227, 223; ruby spinelle, ruby balais, almandine ruby, goutte de sang, ib.; im- itation, 229. Stalactite, 73, '365; described, 380. Stalagmite, 73 ; described, 380. Star facets, 162. Star of the south, 210. Staurolite, 66. Stephanite, 66. Stilbite, 48, 56. Strahlstein, fusibility of, 115. Striae, 55. Strontia, test of, 122. St Stephen's stone (chalcedony), 278. Stygmite, a carnelian, 281. Sulphate of baryta, 87. Sulphur, 48; refraction of, fc7 ; test for, 118. Sunstone, sapphire, 216; iridescence of, 93; adnlaria, 313. Systems of crystals, 21. T. Table of a diamond, 161. Table diamond, 163. Talc, hardness of, IS. Tantalium, test ot, 128. Tchingtching (lapis lazuli). 325. Tellurium, test ot, 124. Tenacity of minerals, 80. Terminology, 19. Tesseral, or tessular system, 21 ; described, 82. Tetragonal system, 21, 34; closed forms, 35 ; tetragonal pyramids, ib.; ditetrago- nal, ib.; tetragonal sphenoids, 36; tet- ragonal scalenohedrons, ib.; open forms, 86 ; tetragonal prisms, ib. Tetragonal crystals, how distinguished, 87. Tetrahedral form, 28 ; its sign, 29. Tetrakishexahedrons, 24 ; sign ot, 27. Thorina, test of, 123. Thumerstone, or axinite, 31L Tin, test of, 125 ; tin ore, 64. Titanium, test of, 129. Topaz, crystal, 48; hardness, 80; optical power, 87; electric, 99; a real gem, 136; description of, 229; varieties, 230 ; cutting of, 231; localities, 232; imita- tions, 233; engraved topazes, ib.; topaz of the ancients, 229, 234. Topazolite, 250. Tourmaline, 55, 56; double refraction oft 88; polarization of light, 89; real gem, 136; described,- 254; composition of, 255; 1. Siberian (siberite, rubellite, apy- rite), ib.; 2. Indicolite (Brazilian sap- phire); S.Brazilian (emerald); 4. Ceylon (chrysolite) ; 5. Electric schorl, 256 ; lo- calities, ib.; fine, specimens, ib.; not lyn- curium of the ancients, 258. Triakisoctahedron, sign o^ 27. Triclinohedrie system, 21, 52; pyramids, 53 ; combinations, ib. Trigonal dodecahedrons, 28 ; sign, 29. Tufa, calcareous spar, 365. Tungsten, test of, 128; see Wolfram. Turquoise, hardness of, 80 ; described, 329 ; 1. true oriental; 2. bone, or occiden- tal, 330. u. Ultramarine, made from lapis lazuli, 324; how prepared, 325; imitations, 826. Uranium, test ot; 128. Y. Vanadium, test of, 128. Variolite (felspar), 814. Venus' hair, 261. Volcanic glass, or obsidian, 80fc 4G4 INDEX. W. Water in rock crystal, analysis of, 265. Weiss and Rose, system of crystalliza- tion, 21. Wernerite, double refraction o 88. Wolfram, 68; test of, 120; see Tungsten. Wollaston's goniometer, 58. uroodstone, 2TT. Yttria, test of, 128. z. Zinc, blend, 64 ; test of 124. Zircon, double refraction of, 87; test of 123; described, 244; same as hyacinth ib.; varieties, 245. Zuisang (lapis lasuli), 825. APPENDIX. CHRONOLOGICAL LIST OF WORKS ON GEMS AND MINERALS SINCE THE FIFTEENTH CENTUBY. BECHAI, (Ben Ascliar,) Biur al Hattorah, (Exposition of the Law of Moses,) a Commentary on Exodus xxviii. 17-20* A. M. 5207, (A. D. 1447.*) Plinii secundi, (Caii,) Naturalis Historia. Fol. Venice, 1469. Aristotle, Lapidarius, de novo e Graeco translatus. Lucas Brandis. 4to. Eegia Mer&ourg, 1473. Serapion, (John,) De Medicamentis tarn simplicibus quam compositis. Mediolanum, 1473. Alberti, (Magni,) Philosophorum maximi de Mineralibus. Libri V. Patavii, 1476. Avicenna, (Abou-Ali-Alhussein-Ben-Adloulah,) Canones Medicinae, Latt. reddit. Venice, 1483. Csesalpinus, (Andreas,) De Metallicjs Libri tres. 4to. Rom. 1496. Leonardus, (Camillus, M. D.,) Speculum Lapidum. 4to. Venet. 1502. * This work contains an ample account of the properties of precious stones. The edition of 1447 is the earliest, but it has since been many times re- printed. 466 APPENDIX. Aben Ezra, (Rabbi,) Commentarium in Decalogum. 8vp. Hehr. Basel, 1527. Rue, (Franc, de la,) De Gemmis. 8vo. Parisii, 1547 ; 8vo. Lugd. 1622 ; 12mo. Franc. 1626 ; 12mo. Gron. 1626. Agricola, (G.,) De Re Metallica, Libri XI. ; et de Natura fossijium, Libri X. Fol. BasUice, 1546. Ruens, (F.,) De Gemmis aliquot, iis prsesertim quarum Divus Joannes Apostolus in sua Apocalypsi notavit. 8vo. Paris, 1547. Libravii (Andr.,) Singularium libr. IV. quorum I. et III. de metallis lapidibus, et fossilibus. 8vo. Franco/. 1549 ; also in 1601. Encelius, (Christoph,) De Re Metallica, hoc est, de origine, varietate et natura corporum metallicorum, Lapidum, Geinmarum atque aliarum quae ex fodinis eruuntur Libri III. 8vo. Francf. 1551. Theophrasti, (Eresii,) Opera omnia, Greece, cura Camotii edidit F. Turisanus. 70. Venetus, apud Aldi filios, 1552. Langius, (Johannes,) Epistolse Medicinales. Fol. Lugd. 1557. Agricola, (George,) De Ortu et Causis Subterraneorum. De Natura eorum quse effluunt ex Terra. Fol. Bas. 1558. Mandeville, (John,) Le Grand Lapidaire, ou sont declarez les noms de Pierres orientales, avec les Vertus et Proprietes d'icelles, et iles et pays ou elles croissent. 12mo. Paris, 1561. Porta, (Giov. Baptista,) Magiae Naturalis Libri IV. Antwerp, 1561. Fallopius, (G.,) De Medicatis Aquis atque de Fossilibus, tractatus ab Andrea Marcolino collectus. 4to. Venitia, *1564. Dolce, (Ludovico,) Libri tre, nei quali si tratta delle diverse sorti delle Gemme che produce la Natura. 8vo. Yen. 1564. Rulandus, (Martinus,) Medicina Practica, 12mo. Arg. 1564. Gesneri, (C.,) De omni rerum fossilium genere, gemmis lapidibus, metallis, &c. 8vo. Tiguri, 1565. Leonardus, (Camillus;) Trattato delle Gemme che produce la Natu- ra ; traduzione di M. Ludovico Dobe. 8vo. 1565. Gesner, (Conrad,) Liber de Rerum fossilium, Lapidum, et Gem- marum, maxime figuris, etc. 8vo. Tig. 1565. Epiphanius, De duodecim Gemmis in Veste Aaronis. Gr. Lat. cum corollario Gesneri. 8vo. Tig. 1565. Fabricius, (G.,) De metallicis rebus et nominibus obs. var. erud quibus. ea potissimum explicantur quse G. Agricola praeteriit. 8vo. Tiguri, 1566. Lemnius, (Levinus,) Occulta Naturae Miracula. 8vo. Antwerp, 1567. Mizaldus, (Anton.,) Memorabilium Utilium et Jucundorum Centuria IX. 8vo. V 'APPENDIX. 467 Cellini, (Benvenuto,) Del Arte del Gioiellare. 4to. Fior. 1568. Albert!, (Magni,) De Mineralibus et rebus metallicis. Libri V. 8vo. 1541, 1569. Mizaldus, (Anton.,) Secrets de la Lune. Svo. Paris, 1571. Athenaeus, Deiphnosophistae, (Banquet des Pliilosopb.es,) traduit par Dalecbamp. Paris, 1573. Marbodaaus, (Gallus,) De Gemmarum Lapiduinque pretiosorum for- mis atque viribus opusculum. 8vo. Colon. 1593 ; 12mo. Ba#. 1555 ; 12mo. Lubec, 1575. Belleau, (Rene,) Les Amours et nouveaux Changes des Pierres pre cieuses. 4to. Paris, 1576. Evax, (a King of the Arabs,) a MS. is attributed to him on the properties and effects of precious stones, published by Henry Rantzovius, under the title " De Gemmis scriptum olim a poeta quodam non infeliciter carmine redditum et nunc primum in lucem editum." 4to. Leipsic, 1585. Bacci, (Andrea,) Le XII. Pietre preziose. ' 4to. Roma, 1587. Cnesalpin, (A.,) De re metallica. 4to. Romce, 1596. Porta, (Giov. Baptista,) A Method of Knowing the Inward Virtues of Kings by Inspection. Fol. Neapoli, 1601. Arnobio, (Cleandre,) II Tesoro delle Gioie, trattato maraviglioso. Venet. 1602. ^ Bacci, (Andrea,) De Gemmis et Lapidibus pretiosis, tractatus ex Ital. Lingua Lat. red. 8vo. Franco/, 1605. Fernel, (John Francis^) Pharmacia, cum Guliel. Plantii et Franc. Saguyerii Scholiis. 12mo. Hanov. 1605. Morales, (Gasp, de,) Libro de las Virtudes y Propriedades maravil- losas de las Piedras preziosas. 8vo. Madrid, 1605. Porta, (Giov. Baptista,) De DistiUationibus. 4to. Rome, 1608. Avicennaa Opera. Roma?, 1593. Venetiis, 1608. Ferrante Imperator : De fossilibus opusculum. 4to. Napoli, 1610. Portaleone, (Abraham,) Shilte Haggeborim. (The Shields of the Mighty.) Heb. Mantua, (A. M. 5372,) 1612. Clutius, (Augerius,) Calsvee, sive Dissertatio Lapidis Xephrititri, seu Jaspidis viridis, naturam, proprfetates, et operationes exhibens Belgice. 8vo. Amsterdam, 1621, et Lat. per Gul. Lauremberg, fil. 8vo. Rostochii, 1627. Bacci, (Andrea,) De Gemmis ac Lapidibus pretiosis in S. Scriptura. 4to. Rome, 1577 ; 8vo. Franc. 1628. Jonstonus, (Johannes,) Thaumatographia Naturalis. 12mo. Amst. 1632, 468 APPENDIX.* * Clave, (Estienne,) Paradoxes, ou Traittez PMlosopliiques desPierres et Pierreries, centre 1'opinion vulgaire. 8vo. Paris, 1635. Csesius, (Bernardus,) De Mineralibus. Fol. Lugduni, 1636. Toll, (Adrianus,) Gemmarum. et Lapidum Historia. 8vo. Lugduni, 1636. Boot, (Anselmus Boetius de,) Gemmarum et Lapidum Historia. 4to. Hanover, 1690. Recensuit et commentariis illustravit Adr. Toll. 8vo. Lugd, Batav. 1636. Boot, (Ans. Boe'ce de,) Le Parfaict Joaillier, ou Histoire des Pierreries, de nouveau enriclii de belles Annotations par Andre Toll, trad, du Lat. par J. Bachou. 8vo. Lyon, 1644. Toll, (Adr anus,) Le Parfaict Joiillier, ou Histoire des Pierreries, ou 1 01 1 amplement descrites leur naissance, juste prix, etc. 8vo. Lyon, 1644. Laet, (Jo. de,) De Gemmis et Lapidibus, Lib. II. Gr. et Lat. Part*, 1647. Ecchellensis, (Abraham,) Versio Durrhamani de Medicis Virtutibus animalium, plantarum et Gemmarum. 8vo. Pans, 1647. Habdarralimanus, (Asiutensis ^Bgyptius,) De Proprietatibus ac Vir- tutibus medicis Animalium, Plantarum ac Gemmarum, ex Arab. Lat. redd, ab Abrahamo Ecchellenst 8vo. Paris, 1647. Laet, (John de,) De Gemmis et Lapidibus Libri II., quibus prsemit- titur Theophrasti Liber ; de Lapidibus Gr. Lat., cum Annotationi- - bus. 8vo. Ludg. Bat. 1647. Boetius, (de Boot,) Gemmarum et Lapidum historia, quam olim edidit Ans. B. de Boot, postea Adrianus Tollins recensuit. Tertia Edit, longe purgatissima. Cui accedunt Jo. de Laet, de gemmis et lapidibus Libri II., et Theophrasti liber de Lapidibus. 8vo. Lugduni Batawrum, 1647. Paracelsus, (Philippus Aurelius Theophrastus,) Nine Books on the Nature of Things ; into English by J. F. 4to. London, 1650. Nichols, (Thomas,) Arcula Gemmea ; or, the Nature, Virtue and Valour of Precious Stones, with Cautions for those who deal in them. 4to. Cambridge, 1652. Nichols, (Thomas,) A Lapidary, Vr History of Pretious Stones ; with Cautions for the undeceiving of all those that deal with Pretious Stones. 4to. Cambridge, 1652. Hermes Trismegistus, Tabula Smaragdina vindicata. 12mo. 1657. Nichols, (Thomas,) Gemmarius Fidelis, or the Faithful Lapidary ; experimentally describing the richest Treasures of Nature, in an Historical Narrative of the several Natures, Virtues and Qualities APPENDIX. 469 of all Precious Stones, "with a Discovery of all such as are Adul- terate and Counterfeit. 4to. London, 1659. Lowell, (Robert,) Panzoologicomineralogia, or a History of Animals and Minerals. 12mo. Oxford, 1661. Johnson, (J.,) Notitia regni mineralis, sive Catalogus subterraneorum cum prsecipuis differentiis. 12mo. Lipsice, 1661. Berquen, (Robert de,) Les Merveilles des Indes Orientales et Occi- dentales, ou nouveau Traite des Pierres precieuses et des Perles. 4to. Pflrw,.1661. Jonstonus, (J.,) Notitia Regni Yegetabilis et Mineralifl. 12mo. Lips. 1661. Boyle, (Hon. Robert,) Experiments and Considerations upon Colour, with Considerations on a Diamond that Shines in the Dark. 8vo. London, 1663. Kircheri, (Athanasii,) Mundus subterraneus in Libros XII., digestus. With plates and portraits of Kircher and Pope Alexander. Fol. . Amsterdam, 1665. Histoire des Joyaux et des principales Richesses de 1'Orient et de 1'Occideat. 12mo. Geneve, 1665. M. L. M. D. S. D., Denombrement, FacultS et Origine des Pierres precieuses. Post 8vo. Paris, 1667. Schmid, (Joachimus,) De Margaritis. 4to. Wtttebergce, 1667. Rhosnel, Le Mercure Indien. Paris, 1668. Piererus, (G. P.,) Lazulus, Dissertatio chymico-medica. 4to. Ar- gentarati, 1688. Aldrovandi, (Ulyssis,) Opera Omnia. 3 vols. fol. with several thou- sand wood cuts. B&nonice, 1599-1668. Tesoro deUe Gioie, Trattato Curioso. 12mo. Venetia, 1670. History of Jewels. 12mo. London, 1671. Steno, (Nicolaus,) Prodromus to a Dissertation concerning Solids naturally contained within Solids. London, 1671. Boyle, (Hon. Robert,) An Essay about the Origin and Virtues of Gems, with some Conjectures about the Consistence of the Matter of Precious Stones, etc. London, 8vo. 1672, and 12mo. 1673. Sandius, (Christopher,)* On the Origin of Pearls. Phil. Trans. 1674. Tavernier, Voyages en Turquie, enj'erse et aux Indes. 4to. Paris, 1676. Kircher, (Athanasius,) Mundus Subterraneus in XII. Libros digestus. Fol. Ainstellodami, 1678. Blumenberg, Dissertatio Medica de Succino. 4to. Jena, 1682. 470 APPENDIX. Kirani, Kiranedes, et ad eas Rhyakini Koronides, sive Hysteria Physico-Medica. 12mo.. London, 1685. Konig, (Emanuel,) Regnum Minerale, physice, inedice, anatomice, alcliymice, analogice, tlieoretice et practice investigatum. 4to. Basil, 1687. Orpheus, (1260 B. C.,) Hymni et de Lapidibus, Gr. Lat., curante A. C. Eschenbachio ; accedunt H. Stepliani notae. 8vo. Traj. ad Rh. 1689. Panthot, (Jean B.,) Trait e des Dragons et des Escarbqucles. Small 12mo: Lyon, 1691. Hiaerne, (Urban,) Kort Anledning til askillige Malm och Bergarters, Mineraliers, etc. ; eftersporjande och angifvande. Stockholm, 1694. Hiller, (Matth.,) Tractatus de Gemmis XII. in Pectorali Pontificis Hebraeorum. 4to. Tubingen, 1698. Slevogtii, (J. H.,) De Lapide Bezoar. 4to. Jena, 1698. Venette, (Nicolas,) Trait6 des Pierres. 12mo. Amst. 1701. Strachan, Observations on Coral, large Oysters, Rubies, etc. Abr^ ii. 711. Phil. Trans. 1701. Gulielmini, De Salibus dissertatio physica, medico-mechanica. Ve- netiis, 1705. Curiose Speculationen. Leipzig, 1707. Description of the Diamond. Phil. Trans. Abr. ii. 405. 1708. Chambon, Traite des Metaux et des Mineraux. 12mo. Paris, 1714. Leisnerus, (Gott. Christ.,) De Coralliorum Natura, Proeparatis et Usibus. Wittembergw, 1720. Cappeller, (Maur. Ant.,) Prodomus Crystallographise, de Crystallis iinproprie sic dictis Commentarium. 4to. Lucernce, 1723. Henckel, (J. Fr.,) Pyritologia. 8vo. Lip&im, 1725. Woodward, (Dr. J.,) Fossils of all kinds digested into a method suit- able to their mutual relation and affinity. With plates. London, 1728. Woodward, (Dr. J.,) An attempt towards the Natural History of the Fossils of England, in the collection of J. Woodward. 8vo. Lon- don, 1729. Memoires de Regne de Catherine, Imperatrice de Russie. Amster- dam, 1729. Bourget, Lettres sur la Formation des Sels et Cristaux. 12mo. % Amst. 1729. Bromel, (Magn. von,) Inledning til nodig Kundskap om Bergarter, Mineralier, Metaller, samt Fossil ier. 8vo. Stockholm, 1730. APPENDIX. 471 Gimma," (D. Giacinto,) Delia Storia naturale dell^ Gemme, delle Pietre e di tutti Mineral!, owero della Fisica sotteranea. 4to. Napoli, 1730. Sarmento, (James Castro de, M. D.,) An Account of Diamonds found in Brazil. Phil. Trans. Abr. vii. 503. 1731. Henckel, (J. Fr.,) Idea generalis de Lapidum origine. 8vo. Dresd. et Lips. 1734. Colonne, (Francois Marie Pompee,) Histoire Naturelle de TUnivers. 4 vols. 8vo. Paris, 1734. Pluche, (1'Abbe Antoine Noel de,) Spectacle de la Nature. 4to. Paris, 1732-39. Becher, (John Joachim,) Physica Subterranea. 4to. Lipsice, 1739. Argenville, Traite de 1'Oryctologie. Paris, 1740. Marbodaeus, De Lapidibus pretiosis Enchiridion, cum Scholiis Pic- torii. 4to. Wolfenbuttelce, 1740. Swedenborgii, (Emanuelis,) Opera Philosophica et Mineralia. 3 vols. fol., with numerous plates. Paris, 1743. Argenville, (A. J. D. d',) De 1'Histoire Naturelle eclaircie dans deux de ses parties principales : la Lithologie et la Conchologie. 4to. Paris, 1743. Elliott, (John, F. R. S.,) on the Specific Gravity of Diamonds.' Phtt. Trans. Abr. ix. 147. 1745. St. Laurent, (Joanon de,) Description abregee du fameux Cabinet de M. le Chevalier de Baillon, pour servir a 1'histoire naturelle des Pierres precieuses, etc. Luques, 1746. Theophrastus, History of Stones, with the Greek Text and an Eng- lish Version, and Notes Critical and Philosophical, including the Modern History of Gems described by that Author, by Sir John Hill. 8vo. London, m$. Kahler, (Mart.,) De Crystallorum Generatione. 4to. Upsal,174X. Henckel, (J. Fr.,) In Mineralogia redivivus. 8vo. Dresdw, 1747. Wallerius, (J. G.,) Mineralogia eller Mineral Ricket indelt och besk- rifvet. 8vo. Stockholm, 1747. Dingley, (Robert, Esq.,) On Gems and Precious Stones, particularly such as the Ancients used to engrave on. Phil. Trans. Abr. ix. 345. 1747. Hill, (Sir 'John,) The History of Fossils. London, 1748. Leonardus, (Camillus,) The Mirror of Stones, in which the Nature, Generative Properties, Virtues and Various Species of more than 200 different Jewels, Precious and Rare Stones are distinctly described. 8vo. London, 1750. 472 APPENDIX. Mariette, (P. J.^ Trait6 des Pierres gravies. Fol. Paris, 1750. Jeffries, (David, Jeweller,) Treatise on Diamonds and Pearls, in which their importance is considered, plain rules are exhibited for ascer- taining the value of both, and the true method of manufacturing Diamonds is laid down. 8vo. 30 copper plates. Published by subscription. London, 1750-51 and 1753. Jeffries, (D.,) Trait6 des Diamants et des Perles. 8vo. . Paris, 1753. Pott, (M. J.,) Lithogeognosie, ou Examen chymique des Pierres et des Terres en general et de la Topaze et de la Steatite en particu- lier. 8vo. Paris, 1753. Jeffries, (David,) An Abstract of the Treatise on Diamonds and Pearls, by which the usefulness to all who are any way interested in these jewels will sufficiently appear, and therefore addressed to the nobility and gentry of this kingdom, and to the traders in jewels. 8vo. Baldwn, London, 1754. Natter, (Laurentius,) A Treatise on the Ancient Method of Engrav- ing Precious Stones compared with the Modern. Fol. London, 1754. Traite des Pierres _de Theophraste, trad, du Grec. 12mo. Paris, 1754. Salerne, L'Oryctologie. 4to. Paris, 1755. Cartheuser, Elementa Mineralogise systematice disposita. 8vo. Fran- co/. 1755. Kalm, (P.,) Nagra Kannemarken til nyttiga Mineraliens eller ford och Baigarters upfinnande. 4to. Aboce, 1756. Da Costa, (E. Mendes,) Natural History of Fossils. 4to. London, 1757. Pott, (J. H.,) Chemische tlntersuchungen, welche vornehmlich von der Litheognosie handeln. 4to. Potsdam, 1746 ; also 1751-54 and 1757. Woltersdorf, (J. L.,) Systema minerale in quo regni mineralis pro- ducta omnia systematica per classes, ordines, genera, et species proponuntur. 4to. Berlin, 1738 ; also 1753-4, and 1755-8. Cronstedt, (Axel von,) Forsok til Mineralogia eller Mineral-rikets Up- stallning. 8vo. Stockholm, 1758. Bomare, (Valmont de,) Prospectus d'un cours surl'histoire.Naturelle des Mineraux. 12mo. Paris, 1759. Gerhard, (C. A.,) Disquisitio physico-chemica Granatorum Silesiae atque Bohemise. Inaug. Diss. 4to. Frankfurt a. d. Oder, 1760. Gronovii, (L. T.,} Bibliotheca Regni Animalis et Lapidei. 4to. Luyd. Bat. 1760. APPENDIX. 473 Natter, (Lgurentius,) Catalogue des Pierres gravies de My lord Comte de Besborougli. 4to. London, 1761. Pouget, (N.,) Traite des Pierres precieuses, et de la maniere de les employer en parure. 4to. Paris, 1762. Vogel, (R. A. Praes.,) Terrarum atque lapidum partitio, resp. A. Fr. Hempel. 4to. Gdttingen, 1762. Walch, (J. E. J.,) Das Steinreich systematischentworfen. 2 vols. 8vo. 24 plates. Halle, 1762. Bertrand, (E.,) Dictionnaire universel des fossiles propres et des fossiles accidentels, contenant une description des Terres Sables, &c. 8vo. 2 vols. in 1. La Haye, 1763. 'Pheopliylacti Opera, a J. F. Bern, de Rubeis et Borif. Finettio, Greec. et Lat. 4 vols. Fol. Venet. 1754 and 1763. Justi, (J. H. G.,) Grundriss des gesammten Mineralreiclis. 8vb. Gdttingen, 1757 ; also in 1765. Linnaeus, (C.,) Systema Naturae sive tria regna. Ed. I. Fol. Lugd.. Bat. 1735. Ed. XII., Holmice, 1766. Bertrand, (E.,) Recueil de divers TraiteV sur 1'Histoire Naturelle de la Terre et des Fossiles. 4to. Avignon, 1766. Bock, (Fr. S.,) Vesucb einer kurzen Naturgeschicbte des Preussischen Bernsteins, und einer neuen warscbeinlichen Erklarung seines Ursprunges. 8vo. Kdnigsberg, 1767. ' Wallerius, (J. G.,) Lucrubrationum arademicarum specimen primum de systematibus mineralogicis et systemate mineralogico rite condendo. 8vo. Holmice, 1768. * Scopoli, (J. -A.,) Einleitung zur Kenntniss und Gebrauch der Fos- silien. 8vo. Riga und Milan, 1769. Baumer, (John Willi^ Historia Naturalis Lapidum preciosorum omnium, etc. 8vo. Franc. 1771. Bourguet, Du Regne Minerale. 4 vols. 12mo. Paris, 1771. Forster, (J. R.,) ClassiJBcation of Fossils and Minerals. London, 1768 ; also in 1772. Scopoli, (J. A.,) Principia Mineralogiaa systematic^ et practical. Pragcs, 1772. Juwelier, Der Aufrichtige, oder Anweisung aller Arten Edelsteine, Diamanten, und Perlen zu erkennen, nebst einer aus dem Engliscben iibersetzten AbbandJung von den Diamenten und Perlen. 8vo. Frankfurt, 1772. Hodgson, (Rev. Jobn,) Dissertation on an Ancient Cornelian. ArcJwol. ii. 42. 1773. 474 APPENDIX. Bruckmann, (U. F. B.,) Abhandlung von Edelsteinen. Braunschweig, 1757-73. Baiimer, (J. W.,) Naturgeschichte aller Edelsteine, wie auch der Erde und Steine, so bisher z'ur Artznei sind gebraucht worden. Aus dem Latein. von Karl, Freih. von Meidinger. 8vo. Wien, 1774. Schroter, (J. S.,) Journal fiir die Liebhaber des Steinreichs. Weimar, 1774. Werner, (Abr. G.,) Vender ausserlichen Kennzeichen der Fossilien. 8vo. Leip. 1774. Bruckmann, (Fr. Hier.,) A Treatise on Precious Stones. 8vo. 1775. Born, (Baron Inigo,) Schneckensteine, oder die Sachsischen Topas- felsen. 4to. Prag. 1776. Collini, (Cosmus,) Journal d'un Voyage, qui contient differentes observations rnineralogiques, particulierement sur les agates, avec . un detail sur la maniere de travailler les agates. 8vo. Manrilieim, 1776. Dutens, (Lewis,) Des Pierres precieuses et des Pierres fines, avec les moyens de les connoitre et de les valuer. Londres, 1776. Scopoli, (Jo.,) Ant. Crystallographia Hungarica. 4to. Prague, 1776. Vogel, (R. A.,) Practisches Mineralsystem. 2d ed. 8vo. Leip. 1776. Sage, Mineralogie docim'astique, with plates. 8vo. Paris, 1772 ; also in 2 vols. in 1777. Wallerius, (J. G.,) Systema Mineralogicum, quo Corpora Mineralia in classes, ordines, genera et species, suis cum va'r. divisa descri- buntur atque observationibus, experimentis et figuris illustrantur. 2 vols. 8vo. Vindob.l. Bruckmann, (U. F. B.,) Gesammelte und eigane Beitrage zu seiner Abhandlung von Edelsteinen. Braunschweig, 1778. Bomare, (Valmont de,) Mineralogie, ou nouvelle exposition de Regne Minerale. 8vo. Pa/ris, 1769 ; also in 1774, 1780. Fichtel, (J. C. Von,) Mineralgeschichte. 4to., with plates. Ham- burgh, 1780. Haiiy, (Abbe de,) Traite de la Mineralogie. Paris, 1780. Regenbogen-Achat, Vom. 4to. Hamburgh, 1780. Gerhard, (C. A.,) Beitrage zur Chemie und Geschichte des Mmeral- reichs. 2 vols. 8vo. Berlin, 1773-1776 ', also in 1781. Lenz, (J. G.,) Tabellen iiber das gesammte Steinreich. 4to. Jena, 1781. Bergmann, (T.,) Sciagraphia regni mineralis secundum principia proxuna digesti. 8vo. Lipsice, 1782. APPENDIX. 475 jjj Buchoz, Lee Dons merveilleux et diversement colories de la Nature dans le Regne Mineral. Fol. Para,. 1783. (^.rosi, (Johann,) Sur la Generation du Silex du Quarz. 8vo. Oracm. 1783. Rome de L'Isle, Essai de Cristallographie. 8vo. Paris, 1772. 2d ed. in 4 vols. 8vo. 1783. M. Buffon, (Le Comte de,) Histoire Naturelle des Mineraux. 4to. Paris, 1783. Faujas de Saint Fond, (B.,) Mineralogie des Volcans ou Description de toutes les substances produits ou rejetees par les feux souter- rains. Royal 8vo. Paris, 1784. Daubenton, Tableaux methodiqtie des Mine'raux suivant leurs dif- ferentes natures. 4to. Paris, 1784. Ravius, (S. F.,) Specimen Arabicum, continens descriptionem et ex- cerpta libri Achmedis Teifascbii ' De Gemmis et Lapidibus Pre- tiosis/ Arabic. Trapetum ad Rhenum, 1784. Haiiy, (Rene Just.,) Essay d'une Theorie BUT la structure des Cris- taux. 8vo. Paris, 1784. : - Cadet, (Le Jeune,) Memoire sur les Jaspes et autres Pierres pre- cieuses de 1'ile de Corse, etc. 8vo. Bastia, 1785. Genuine Account of the present state of the Diamond Trade in the Dominions of Portugal, with some authentic pieces, in a letter from a merchant in Lisbon to his Correspondent in London. 4to. Lr. xviii 368. 1798. Struve, (H.,) Methode Analytique desFossiles, fondee surleurs Carac- teres Exterieurs. 8vo. Lausanne, 1797 ; 8vo. Paris, 1798. Townson, (R.,) Philosophy of Mineralogy. 8vo, Plates. London, 1798. Reuss, (F. A.,) Lexicon Mineralogicum, sive Index Latino-Gallico- Suecico-Danico-Angnco-Russico-Hungarico-Germanicus Minerali- *mn. 8vo. Cura Regis. Leip. 1798. GreviUe, (Rt. Hon. Charles, F. R. S.,) On the Corundum Stone from Asia. Phil.- Tram. Abr. xviii. 356, 1798, and NicJi. Journ, ii, 477. 1799. Guyton-Morveau, (B. L.,) Verbal Process of the conversion of Soft Iron into Cast Steel by means of the Diamond. Nich. Journ. iii. 353. 1799. Klaproth, (Martin Henry,) Analysis of the Spinel. Nich. Journ, iii. 549. 1799. Palm, (J. J.,) Dissertatio gradualis sistens observationes nonnullas de Lapide Obsidiano. 4to. Londoni Gothorum, 1799. Babington, A Systematic Arrangement of Minerals. 4to. London, 1795 ; 1799. Batsch, (A. J. G. K.,) Versuch einer Anleitung zur Kenntniss und Geschiehte der Thiere und Mineralien. 2 Bde. 8vo. Jena, 1788, 1789 ; also 1796-1800. Jameson, (Robert,) Mineralogy of the Scottish Isles. Maps and Plates. 2 vols. 4to. Edinburgh, 1800. Brunner, (J.,) Versuch einer neuen Systems der Mineralogie. 8v r o. Leipzig, 1800. Blindheim, (J. J.,) Ueber den Sibirischen und Taurischen Kalzedon. Neue Schrift. der GeseUsch. naturf. Freunde. 4to. Berlin, 18CO. 478 APPENDIX. Mackenzie, (Sir Geo. Stewart, Bart., F. R. S. L. & E.,) Experiments on the Combustion of the Diamond, the Formation of Steel by its Combination with Iron, etc. Nich. Journ. iv. 103. 1800. BournoH, (Count de,) Description of the Corundum Stone, and its Varieties commonly known as Oriental Ruby, Sapphire/ e.tc. Phil. Trans, p. 223. 1801. Kohler, (H. K. A. von,) Untersuchung iiber den Sard, Onyx, und Sardonix. 8vo. Braunschweig, 1801. ' ,-V Ur, (Fr. Ben.,) Ueber den Sarder Onyx und Sardonyx ; also, Nach- trag iiber, etc., 1804. Braunschiceig, 1801. Hoff, (A. von,) Magazin fur die gesammte Mineralogie, &c., pi. 8vo. Leipz. 1801. Haiiy, (L'Abbe,) Traite de Mineralogie. 8 vols. 8vo. Paris, 1801-2. Ma we, Mineralogy of Derbyshire. 8vo. Plates. London,. 1802. Dolomieu, (D. de,) Sur la Philosophic Mineralogique et sur Fespece Mineralogique. 8vo. Paris, 1802. Klaproth, (Martin Heinrich,) Beytrage zur Chemischen Kenntniss der Mineralkorper. 3 B. 8vo. Berlin, 1795-1802. Biehle, (Von,) Ueber die Bernstein-Grabereien in Hinter-Pommeru. 8vo. Berlin, 1802. Chenevix, (Richard, Esq., F. R. S.,) Analysis of Corundum and some Substances that accompany it. Phil. Trans, p. 327. 1802. Haiiy, Memoire sur les Topazes du Bresil. Ann. du Mus. Paris, 1802. Schwarze, (Christ. Aug.,) De Smaragdo Veterum. 4to. Gorlicii, 1802. Lenk, (J.,) Neue Entdeckung eines Steines Serpentin-Agat. Wie?i, 1802. Gregor, (Rev. William, M. A.,) An Analysis of a variety of the Co- rundum. Nich. Journ. iv. 209. 1803. Schwarze, (Christ. Aug.,) De quodam Pseudo-Smaragdorum apud veteres genere. 4to. Gorlicii, 1803. Hausmann, (J. F. L.,) Krystallogische Beitrage. 4to. PL 1803. Ludwig, (C. F.,) Handbuch der Mineralogie nach A. G. Werner.- 8vo. Leipzig, 1803. Lucas, (J. A. H.,) Tableau Methodique des especes minerales. 8vo. Paris and Strasb. 1803. Schwarz, (G. M.,) Handbok i Oryktognosien. 8vo. 1803. Launnas, (L. de,) Mineralogie des Anciens. 2 vols. 8vo. Bruxelles and Paris, 1803. Rozin, Essai sur Fetude de la Mineralogie. 8vo. 368 pp. Bruxelles, 1803. APPENDIX. 479 Mohs, (Priederich,) Handbuch der Oryktognosie. 3 vols. 8vo. Wien, 1804 Accmn, (F.,) Elements of Crystallography, after the manner of Haiiy. 8vo. plates. London, 1804. Accum, (F.,) Analysis of Minerals. 12mo. London, 1804. Suckow, Anfangsgriinde der Mineralogie. 8vo. Leipzig, 1790 ; 2d ed. 2 vols. 8vo. 1803-4. Haberle, (C. C.,) B^eobachtungen iiber die Gestalt der Grand und Keimkrystalle des schorlartigen Berylls, nnd dessen iibrige. oryctognostiche und geognostische Verhaltnisse. Erfurt, 1804. Meineke, (J. L. G.,) Ueber den Chrysopras und die denselben beg- leitenden Fossilien in Schlesien. 4to. Erlangen, 1805. Jameson, (Robert,) A Treatise on the External Characters of Minerals. 8vo. Edinburgh and London, 1804-1805. Haberle, (C. C.,) Beitrage zu einer allgemeinen Einleitung in das Studium der Mineralogie. 8vo. Weimar, 1805. Haberle, (C. C.,) Characterisirende Darstellung der Mineralien mit Hinsicht auf Werner et Hauy's beobachtungen. 8vo. Weimar, 1806. Reuss, (F. A.,) Lehrbuch der Mineralogie nach Karsten's Tabellen. 8vo. Leipzig, 1801-1806. Flade, (C. G.,) De Re Metallica Midianitarum et Phoenicorum. 4to. Leipzig, 1806. Berzelius, (J. Jacob, M. D., F. S. A.,) On the Composition of the Topaz, etc, Nich. Journ. ix. 105. 1807. Brongniart, Traite de Mineralogie, avec application aux Arts. Paris, 1807. Eckennan, (N.,) Electra, oder die Entstehung des Bernsteins. 4to. Halle, 1807. Pepys, (William Hasledine, Treasurer of the Geol. Soc.,) On the Quantity of Carbon in Carbonic Acid, and on the Nature of the Diamond. Phil. Trans, p. 267, and Nich. Journ. xix. 267. 1807. Brochant de Villiers, (A. J. M.,) Traite Elementaire de Mineraux suivant les principes de Werner. 2 vols. 8vo. Paris; also 1807. Leonhard, (C. C.,) Taschenbuch fur die gesammte Mineralogie mit Hinsicht auf die neueste Entdeckungen. 8vo. 1807. Accum, (F.,) Manual of Analytical Mineralogy. 2 vols. PI. London, 1808.- ^ Karsten, (D. L. G.,) Tabellarische Uebersicht der mineralogischen einfach.en Fossilien. 8vo. 2te. Aufg. Berlin, 1792 ; also 1800, 1808. ' 480 APPENDIX. Bournon, (Le Comte de,) Trait e de la Chaux Carbonate et do 1'Arragonite, auquel on a joint une introduction a la Mineralogie en general, une Theorie de la Crystallisation et son Application. 4to. Londres, 1808. Brard, (C. P.,) Traite des Pierres precieuses. Paris, 1808. Haiiy, Sur la Reunion de la Pycnite avec le Topaze. 4to. Pans, 1808. Gautier, (J.,) Untersuchung fiber die Entstehung^, Bildung und den Bau des Cbalcedons, etc. Jena, 1809. Hausmann, (J. F. L.,) Entwurf eines Systems der unorganisirten Naturkorper. 8vo. Cassel, 1809. . Weiss, De indagando formarum crystallinarum cliaractere geometri- co principal!. Lipsice, 1809. Lenz, (J. G.,) System der Mineralkorper. 8vo. Bamberg und Wurzb. 1800 ; also in 1809. Petzl, (J.,) Ueber den glatten'Beryll von Rabenstein im Bayrischeri Walde. Abb. der Kon. Akad. 4to. Munchen, 1809-1810. Guyton-Morveau, (B. L.,) On the singular Crystallization of the Diamond. Nich. Journ. xxv. 67. 1810. G lithe, (J. M.,) Ueber den Asterios-Edelstein des Cajus Pliniiis Secundus ; eine antiquarisch-lithognostische Abhandlung. 4to. Munchen, 1810. Fischer, (G.,) Essai sur la Turquoise et sur la Calaite. Moscou, 1810. Accum, (F.,) System of Mineralogy and Mineralogical Chemistry. 4 vols. 8vo. London, 1810. Dree, (Marquis de,) Catalogue de Musee Mineralogique. 4to. Paris, 1811. Maculloch, (John, M. D., F. 'L. S.,) Remarks on. Several Parts of Scotland which exhibit Quartz Rocks, and on the Nature and Connection of this Rock in general. Geol. Trans, i. 450. 1811. Chenevix, (R.,) On Mineralogical Systems. 8vo. London, 1811. Silliman, (B.,) Mineralogy and Geology of New-Haven, in a statistical account of the City of New-Haven, by Pres. Timothy Dwight, published by the Connecticut Academy of Arts and Sciences. 8vo. New-Haven, 1811. Niizlein, (F. A., Versuch eine neuen Systems der mineralogisch- einfachen Fossilien. Bamberg and Wurzburg, 1810, 1812. Lenz, (J. G.,) Erkenntnisslehre der Anorganischer Naturkorper. Giesen, 1813. APPENDIX. 481 Lucas, (J. A. H.,) Tableau Methodique des Especes Minerales. 8vo. Paris, 1806-1813. Bournon, (Comte de,) Catalogue de sa collection Mineralogique. 8vo. with 4to. plates. 1813. Mawe, (John,) A Treatise on Diamonds and Precious Stones, in- cluding their History, Natural and Commercial. To which is added some account of the best method of cutting and polishing them. 8vo. London, 1813. Brewster, (Sir David,) On the Optical Properties of Sulfuret of Car- bon, etc., with Inferences respecting the Structure of Doubly-re- fracting Crystals. Fol. Edinb. 1814. Davy, (Sir Humphry,) Prof, of Chem., etc., etc., Some Experiments on the Combustion of the Diamond and other Carbonaceous Sub- stances. Phil. Tram. p. 557. 1814. Aiken, (Arthur,) Manual of Mineralogy. 8vo. London, 1814. Allan, Mineralogical Nomenclature. 8vo. London, 1814. Gravenhorst,(J.L.C.,) Handbuchder Anorganognosie. 8vo. Leipzig, 1815. Berzelius, (J. J.,) Versuch durch Anwendung der elektrisch chemis- chen Theorie und der chemischen Verhaltnisslehre, ein rein wis- eenchaftliches System der Mineralogie zu begriinden. Aus dem Schwed von Dr. A. F. Gehlen. 8vo. Niirnberg, 1815. *Aikin, (A.,) Manual of Mineralogy. 12mo. Philadelphia, 1815. Bournon, (C. de,) A Descriptive Catalogue of Diamonds in the Cabi- net of Sir Abraham Hume. 4to. London, 1815. Brewster, (Sir David,) On a New Optical and Mineralogical Property of Calcareous Spar. 4to. Edinb. 1815. Hauy, Observations sur les Tourmalines, particulierement sur celles qui se trouvent dans les Etats-TJnis. Mem. du Mus. Paris, 1815. John, (J. F.,) Naturgeschichte des Succins, oder des sogenannten Bernsteins. 8w>. Koln, 1816. Swedenstierna, (E. T.,) An Account of the Swedish Corundum, from Gellivara, in Lapland. Geol. Trans, iii. 415. 1816. Svedenstjerna, (E. Th.,) Ueber den Korund zu Gellivara in Lapland, ubersetzt von Dr. Hessel. Leonh. Taschenb. Frankfurt-a.-N. 1816. Berzelius, (J. J.,) Neues System der Mineralogie, aus dem Schwedis- chen von Dr. Gmelin und Pfaff. 8vo. Nurnberg, 1816. * Reprinted foreign works arc indicated by an asterisk. 482 APPENDIX. Tondi, Element! di Orittognosia. 2 vols. 8vo. Napoli, 1817. Haiiy, (L'Abbe,) Trait e des caracteres physique des pierres. 8vo. figs. Paris, 1817. Sowerby, Britisli Mineralogy. 8vo. London, 1802-1817. Leonhard, (C. C.,) R. F. Menz, und J. H. Kopp, Systematisch-Tabel- larische Uebersiclit und Characteristik der Mineralkorper. 2 vols. Fol. Frankfort, 1806 ; 2d edit. 1817. *Phillips, (Wm.,) Outlines of Mineralogy and Geology. 12mo. New- York, 1817. Zappe, Mineralogische Abliandlungen. Wien, 1817. Haiiy, (Rene Just.,) Traite des Caracteres physiques des Pierres pre- cieuses, pour servir a leur determination lorsqu'elles sont taillees. 8vo. Paris, 1817. Brewster, (Sir David, LL. D.,F.R. S. L.etc,,) On the Optical Proper- ties of Muriate of Soda, Fluate of Lime, and the Diamond, as ex- hibited in their action upon Polarized Light. Phil. Trans, viii. . 157. 1817. Brewster, (Sir David,) t)n the Effects of Compression and Dilatation altering the Polarizing Structure of Doubly-refracting Crystals. 4to. Edirib. 1818. Carton, (J.,) Englischer Juwelier, Kenntniss, Werthund Preisschat- zung aller Edelsteine, Perlen und Corallen, ins Deut. iibersetzt nach der 10 ed. 12mo. Ordtz, 1818. Fisher, (G. de Waldheim,) Essai sur la Pellegrina, ou la Perde In- comparable des freresZozima. P amp. Hist. Nat. 8vo. Moscou, 1818. Teifascite, (Ahmed,) Fior di Pensieri sulle Pietre Preziose, opera stampata nel suo originale Arabo di Ant. RainSri. 4to. Firenze, 1818. Jameson, (Robert,) System of Mineralogy. 2 vols. pi. 8vo. Edin- &wr^,1804; 2ded. 1816; 3d ed. 1818. Hoffmann, (C. A. E.,) Handbuch der Mineralogie mit Fortsetzung von A. Breithaupt. 4 vols. Freylerg, 1811-1818. ^Phillips, (Wm.,) Elementary Introduction to the Knowledge of Mineralogy, with notes and additions on American Articles, by Samuel L. Mitchijl. 12mo. New-York, 1818. Dana, (James Freeman,) Outlines of the Mineralogy and Geology of Boston and its environs. 8vo. Boston, 1818. *Thomson, (Thomas,) System of Chemistry, in 4 vols. Svo., the 3d containing a Treatise on Mineralogy. Edited by Thomas Cooper, from the 5th London edition. PMladelphia, 1818. APPENDIX. 483 Bakewell, (R.,) Introduction to Mineralogy. 8vo. London, 1819. Schoolcraft, (Henry R.,) A view of the Lead Mines of Missouri, including observations on the Mineralogy, Geology, Geography, &c., of Missouri and Arkansaw, and other portions of the Western Country. 2 plates, 300 pp. 8vo. New-York, 1819. Fladung, Versuch iiber die Kennzeichen der Edelsteine und deren vortheilhaftesten Sclinitt. Pesth, 1819. Brochant de Villiers, (A. J. M.,) Sur la cristallisation geometrique- ment et physiquement consideree. With numerous plates. 8vo. Strasburg, 1819. Frischholz, (J.,) Lehrbuch der Steinschneidekunst, fur Steinschneider, Graveurs, etc., und jedens welcher sich iiber die Veredlung der Steine zu unterrichten wiinscht. Mvnchen, 1820. Harris, (Thaddeus M.,) The Natural History -of the Bible, or a description of all the quadrupeds, birds, fishes, &c., precious stones, &c., mentioned in the Bible. 476 pp. 8vo. Boston, 1820. Hausmann, (J. F. L.,) Untersuchungen iiber die Formen der leblosen Natur Ir. Bd. 4to. mit vielen Kupfern. Gottingen, 1821. Mohs, (Friederich,) Die Charaktere der Classen, Ordnungen, Gesch- lechten und Arten, oder die Charakteristik der naturhistorischen Mineral-systems. 8vo. Dresden, 1821. Brard, (C. P.,) Mineralogie appliquee aux arts. 3 vols. 8vo. Paris, 1821. Berzelius, (J. J.,) Von der Anwendung des Lothrohrs in der Chemie und Mineralogie ; Aus der Handschrift ubersetzt von Heinr. Rose. 8vo. Number g, 1821. Berzelius, (J. J.,) The same, translated by J. G. Children. 8vo. 3 pi. London, 1822. Kick, (Z.,) Tentamen JVIineralogicum, seu Mineralium nova distri- butio in classes, ordines, genera, &c. 8vo. BruxeUes, 1821. Koratz, (Michel,) Lexicon Mineralogicum enneaglottum. 8vo. Pest. . 1821. Haiiy, (L'Abbe,) Traite de CrystaUographie. 2 vols. 8vo. Perns, 1822. Haiiy, (L'Abbe,) Traite de Mineralogie. 4 vols. 8vo. Paris, 1822. Cleaveland, (Parker,) Elementary Treatise on Mineralogy and Ge- ology. 670 pp. 8vo. Boston, 1816 ; 2d edit, in 2 vols. 8vo. Bos- ton, 1822. *Lowry, (Delvalle,) Conversations on Mineralogy and Geology. Philadelphia, 1822. Blumhof, (J. C.,) Lehrbuch der Lithurgik. Frankfurt, 1822. Cohen, (M.,) Beschreibendes Verzeichniss einer Sammlung von Dia- manten. Wien, 1822. 484 APPENDIX. Mackenzie, (Sir G. S.,) On tlie Formation of Chalcedony. 4ta PMl. Trans. London, 1832. Partsch, (P.,) Besclireibendes Verzeichniss einer Sammlung von Diamenten und der zur Bearbeitung derselben nothwendigen Ap- parate, etc. Wien, 1822. Neumann, Beitrage zur Kristallonomie. 8vo. Berlin, 1823. Kosk, (M. F.,) Beitrage zur Kenntniss krys tallin Huttenproducte. 8vo. Gdttingen, 1823. Breithaupt,*(A.,) Vollstandige Charakteristik des Mineral-systems. 8vo. Dresden, 1823. Renier, (S. A.,) Element! di Mineralogia. 8vo. Padua, 1823. Phillips, (Wm.,) An elementary introduction to the knowledge of Mineralogy. 8vo. London, 1823. Bellerinan, (J. J.,) Die Urim und Thummin. Berlin, 1824. Glocker, (Ernst Friedrich,) De Gemmis Plinii, imprimis de Topazio. 8vo. Vratislaviai (Breslau,) 1824. Brongniart, (Alex.,) Introduction a la Mineralogie. 8vo. Paris, 1801 ; 2d edit, in 1824. Brard, (C. P.,) Manuel du Mineralogiste. 12mo. Paris, 1808 ; 3d edit. 1824. Steffens, Vollstandiges Handbuch der Oryktognosie. 4 vols. 8vo. Halle, 1811-1824. Stchegloff, (N.,) Mineralpguia po sistemie Gospodinda Haiiy. 2 vols. 8vo. St. Petersburg, 1824. Webster, Catalogue of Minerals in .the State of New-York. 12mo. Albany, 1824. Hall, (Frederick,) Catalogue of Minerals found in the State of Ver- mont, and in the adjacent States. 44 pp. 8vo. Hartford, 1824. Robinson, (Samuel,) Catalogue of American Minerals, with their localities} arranged in the order of the States. 8vo. 316 pp. Boston, 1825. Haidinger, (Wm.,) Treatise on Mineralogy, or the Natural History of the Mineral Kingdom ; translated from the German of Mohs. 3 vols. 8vo. Edinburgh, 1825. Monticelli and Covelli, Atlaute della Mineralogia Vesuviana. 19 pi. Napoli, 1825. Marx, (Dr. C. M.,) Geschichte der Krystallkunde. 8vo. Carlsrulie und Baden, 1825. Ragoumovsky, (Greg. Comte de,) Distribution Technique des Pierres precieuses, avec leurs Caracteres distinctifs. 8vo. Vienne, 1825. APPENDIX. 485 Rose, (G.,) Ueber den Felspath, Labrador, etc., Gilbert, Ann. Leipzig, 1826. Leonhard, (C. C.,) Handbnch der Oryctognosie. 8vo. Heidelberg, 1821 ; 2d edit. 1826. Phillips, (Wm.,) Outlines of Mineralogy and Geology. 3d edit. 8vo. London, 1818 ; 4th edit. 1826. Naumann, (G. FT.,) Entwurf der Lithurgik oder okonomischen Mineralogie. 8vo. Leipzig, 1826. Rau, (Ambros,) Lehrbuch der Mineralogie. 8vo. Wurzberg, 1826. Girardin et Lecoq, Elemens de Mineralogie appliquee aux science chimique. 2vols. 8ro.pl. Paris, 1826. Drapiez, Mineralogie Usuelle, 504 pp. 12mo. Paris, 1826. Blum, (J. R.,) Verzeichniss der geschnittenen Steine indem Konigl. Museum zu Berlin. 8vo. Berlin, 1827. Del Rio, (Don Andres Manuel,) Nuevo sistema M nerale. Mexico, 1827. -,> Bredsdorf, (J. H.,) De notione speciei in regno minerali. 104 pp. 12mo. Copenhagen, 1827. Desnos,(J. O.,) Precis de Mineralogie Moderne. 2 vols. 32mo.pl. formant20 et 21 livr. de TEncyclopedique portative. Paris, 1827. Glocker, (Dr.,) Grundriss der Mineralogie. 8vo. Bredau, 1827. Bernhardi, Beitrage zur Kenntniss der Cristallformen. Erfurt 1827. Comstock, (J. L.,) Elements of Mineralogy, adapted to the use of Seminaries and private students. Ixxvi. and 338 pp. 8vo. Bos- ton, 1827 ; 2d edit. 12mo. Beumenberger, (J. G.,) Der Volkommene Juwelier. Weimar, 1828. Corsi, (Faust,) Delle Piedre antiche libri quattro. Roma, 1828. Fladung, (J. A. F.,) Edelsteinkunde. Sm. 8vo. Wien, 1828. Hausmann, (J. F. L.,) Handbuch der Mineralogie. 3 vols. 8vo. Gottingen, 1813 ; 2d edit. 1828. Breithaupt, (A.,) Physiotegie der Unorganischen Natur. 8vo. pi. Dresden, 1828. Blondeau, Manuel do Mineralogie. 18mo. Paris, 1825 ; 2d edit. 1828. Naumann, (C. Fr.,) Lehrbuch der Mineralogie. 8vo. Berlin, 1828. Freisleben, (J. Ch.,) Magazin fur die Orictographie von sachsen. 8vo. Freib&rg, 1828. Ermann, Beitrage zur Monographie des Marekasit, Turmalin und Brasilianischen Topas. From the works of the Berliner Akad. 4to. Berlin, 1829. 486 APPENDIX. Breithaupt, (A.,) Das Gesclileclit der Rhomboedrischen Turrnaline. Schweizzers Jahrbmh fur Chym. und Phys. 8vo. 1829. Glocker, (Dr.,) Uebersiclit der Krystallisations-systeme, etc. 48 pp. 4tb. Breslau, 1829. Glocker, (Dr.,) Handbuch der Mineralogie fiir Vorlesungen und zum Privategebrauch bestimmt. 1829. Grasman, (J. Gunter,) Zur physischen Krystallonomie, und geomet- rischen Combinationslehre. 8vo. 184 pp. 3 pi. Stettin, 1829. Frankenheim, (M. L.,) De Cristallorum cohaesipne. Breslau, 1829. Haidinger, (Wm.,) Anfangsgrunde der Mineralogie. 15 pi. Leipzig, 1829. Finder, De Adamante Commentatio Antiquaria. Berlin, 1829. Macauley, (James,) A sketch of the Geology and Mineralogy of the State of New-York, pp. 281-362, in a work entitled, " The Na- tural, Statistical and Civil History of the State of New- York, by James Macauley." 3 vols. 8vo. New- York, 1829. Engelhardt, (Ab. von,) Die Lagerstatte der Diamanten im Ural- Gebirge. 4to. Riga, 1830. Lancon, (H.,) L'Art du Lapidaire. Paris, 1830. Schulze, (H.,) Practisches Handbuch der Juwelierkunst und Edel- steinkunde. Quedlinburg und Leipzig, 1830. Vettermann, (A.,) Kurze Abhandlung iiber einige der vorziiglichsten . Classen der Buntsn oder Gefarbten Edelsteine. 8vo. Dresden, 1830. Beudant, (F. S.,) Trait6 elementaire de Mineralogie. 8vo. Plates. Paris, 1834 ; 2d edit, in 2 vols. 8vo. 1830. Naumann, (C. Fr.,) Grundriss der Kystallographie. 8vo. Leipzig, 1826 ; 2d edit. 2 vols. 1830. Glocker, (Dr.,) Handbuch der Mineralogie. 2 vols. 8vo. pi. Nurn- berg, 1831. Kobell, (Frantz von,) Charakteristik der Mineralien. Nurriberg,. 1831. Heseell, Crystallometrie. Leipzig, 1831. Kupffer, Handbuch der rechnenden Kristallonomie. 4to. pi. St. Petersburg, 1831. Karsten, (Dr. C. J. B.,) System der Mineralogie geschichtlich statis- tisch, theoretisch und technisch. 5 vols. 8vo. and royal folio atlas, containing 51 plates. Berlin, 1831. Baldwin, (Ebenezer,) Annals of Yale College, in New-Haven, Con- necticut. 8vo. New-Haven, 1831. Contains a sketch of the Ge- ology and Mineralogy of the vicinity of Yale College. APPENDIX. 487 Proposals of the Phenix Mining Company, with a statement of the History and Character of their Mines in Granby, Conn. 30 pp. 8vo. New-York, 1831. Abich, (H.,) De Spinello, dissert, inaug. chem. 8vo. Berolini, 1831. Parrot^Notices sur les Diamans de 1'Oural. 4to. Mem. de I'Acad. Imp. 9 St. Petersburg, 1832. Walchner, Handbuch der gesammte Mineralogie. 1104 pp. 8vo. Carlsruhe, 1832. Emmons, (Ebenezer,) Manual of Mineralogy and Geology. 230 pp. 12mo. Albany, 1826 ; 2d edit. 299 pp. 12mo. Albany, 1832. Jackson, (C. T.,) and Francis Alger, Remarks on the Mineralogy of Nova Scotia. 1 pi. 115 pp. 8vo. Cambridge, Mass., 1832. Del Rio, (C. Andres,) Elementos de Oryctognosia. ' 8vo. Philadel- phia, 1832. Mohs, (Friederich,) Der Naturgeschichte des Mineralreichs. Wien, 1832. Brard, (C. P.,) .Description historique de sa collection de Mineralogie appliquee aux arts. 8vo. Paris, 1833. Kobell, (Frantz von,) Tafeln zur Bestimmung der Mineralien, etc. 4to. Munich, 1833. Presl, (M. K. B.,) Anleitung zum Selbststudium der Oryctognosie. 8vo. Prague, 1833. Catullo, Element! de Mineralogia applicata alia medicina e alia far- macia. 2 vols. 8vo. Padua, 1833. Rose, (M. Gustav,) Elemente der Krystallographie. 8vo. 10 pi. Berlin, 1833. Uhde, Versuch einer genetischen Entwickelung, &c. A Philoso- phical Essay on the Mechanical Laws of Crystallization. 8vo. 4 pi. Breme, 1833. Prestel, (A. E.,) Anleitung zur perspective Entwerfung, &c. On the Perspective projection of Crystalline forms. 8vo. pi. Gottingen, 1833. Welsh, (Jane Kilby,) Familiar Lessons in Mineralogy and Geology, designed for the use of young persons and Lyceums. 2 vols. 12mo. Boston, 1833. Hitchcock, (Edward,) Report on the Geology, Mineralogy, Botany and Zoology of Massachusetts, made and published by order of that State. 700 pp. 8vo. Amherst, 1833. Cairne, (A.,) La Science des Pierres precieuses appliquee aux arts. Paris, 1833. 488 APPENDIX. Blum, (Dr. Reinliart,) Die Schmuckstejne. Heidelberg, 1828, und Taschenbuch der Edelsteinkunde. 12mo. Stutgart, 1834. Burch, (A.,) Handbuch fiir Juweliere. Weimar, 1834. Ilartmann, (C. F. A.,) Mineralogie. 8vo. pi. llmenau, 1828 ; also in 1834. 9 Hartmann, (C. F. A.,) Repertorium der Mineralogie. 8vo. pi, Leipzig, 1834. Allan, (Robert,) A Manual of Mineralogy. 350 pp. 8vo. Edinburgh, 1834. Suckow, (M. G.,) Grundriss der Mineralogie. 8vo. Darmstadt, 1834. Mather, (William W.,) Sketch of the Geology and Mineralogy of New-London and Windham Counties, in Connecticut. 36 pp % 8vo. with a map. Norwich, 1834. Moore, (N. F.,) Ancient Mineralogy, or an Inquiry respecting Min- eral Substances mentioned by the Ancients. 192 pp. 12mo. New- York, 1834. Porter, (Jacob,) Topographical Description and Historical Sketch of Plainfield, in Massachusetts. 44 pp. 8vo. Greenfield, 1834. Hartmann, (C. F. A.,) Grundziige der Mineralogie und Geologic. 8vo. Nwrnberg, 1835. Richard, (A.,) Precis elementaire de Mineralogie. 8vo. pi. Paris, 1835. Frankenheim, (M. .L.,) Die Lehre von der Cohasion, umfassend die Elasticitat der Gase, die Elasticitat und Coharenz der flussigeii und sesten Korper und die Krystallkunde. 502 pp. 8vo. Breslau, 1835. Necker, Le regne mineral ramene aux methodes de 1'histoire naturelle. 2 vols. in 8vo. of above 400 pages each. Paris, 1835. Thomson, (Thomas,) Geology and Mineralogy, forming the third portion, or the fourth and fifth volumes of his System of Chemistry. 2 vols. 8vo. London, 1835. Shepard, (Charles Upham,) Treatise on Mineralogy, 1st part one vol. 12mo. New-Haven, 1832. 2d part consisting of descriptions of the species, and tables illustrative of their Natural and Chemical affinities. 2 vols. 12mo. with^SOO wood cuts. New-Haven, 1835. Kurr, Grundziige der okonom-techischen Mineralogie. 8vo. 1836. Hochsteller, Populare Mineralogie. 12 pi. 8vo. 1836. *Moffatt, (J. M.,) Mineralogy and Crystallography ; pp. 236-298 of the Scientific Class Book. Reprinted with additions from, the London edition, by Walter R. Johnson. 12mo. Phttadel/phia, 1836. APPENDIX. 489 Gesner, (Abraham,) Remarks on the Geology and Mineralogy of Nova Scotia. 8vo. 272 pp. Halifax, 1837. Dowd, (J. A.,) System of Mineralogy. New-Haven, 1837. Feuchtwanger, (Lewis,) Treatise on Gems. New-York, 1838. Hertz, (B.,) Catalogue of Mr. Hope's Collection of Pearls and Precious Stones, systematically" arranged and described. 4to. London, 1839. Rose, (G.,) De Novis quibusdam Fossilibus quae in montibus Uraliis inveniuntur, Chrysoberillum, Uralium, etc. 8vo. Berobini, 1839. Blum, (J. R.,) Lithurgik, oder Mineralien und Felsarten, nach ihrer Anwendung in Oekon., Artist, und Technischer Hinsicht system- atisch abgehandelt. Stutgart, 1840. Roy, (C. W. van,) Ansichten iiber Entstehung und Vorkommen des Bernsteins, so wie praktische Mittheilungen iiber den Werth und die Behandlung desselben als Handelsware. 8vo. Dantzig, 1840. Konneritz, (L. von,) Mittheilung mannichfaltiger Versuche Edel- steine kunstgemass zu schleifen. Weimar, 1841. Steinbeck, Ueber die Bernstein-Gewinnung. 8vo. Brandenburg, 1841. Petzholdt, (M.,) Beitrage zur Naturgeschichte des Diamantes. 8vo. Dresden und Leipzig, 1843. - Transactions of the Imperial Russian Mineralogical Society at St. Petersburg, 1842. Ramdedsberg, (C. F.,) Chemical Mineralogy. Berlin, 1843. Alger, (Francis,) Elementary Treatise on Mineralogy, by William Phillips. Boston, 1844. Bielhe, (Von,) Bernstein, ein gewichtiges Naturproduct des Konig- reichs Danemark. 8vo. Hamburg, 1845. Haidinger, (W.,) Ueber den Pleochroismus dee Amethysts. Natur- mssenschaftliche Abhandlungen. Wien, 1846. Priifer, (V.,) Ueber die Krytalfonn der Lazulith. 4to. Natur- wissensch. Abhand. Wien, 1847. Goepert, (H. R.,) Ueber Pflanzenahnliche Einschlusse in den Chalce- donen. 8vo. 1848. Haidinger, (W.,) Ueber den Pleochroismus des Chrysoberylls. Berichte iiber Mittheilungen von Freunden der Naturwissenschaf- ten. 8vo. Wien, 1848. Haidinger, (W.,) Ueber eine neue Varietat von Amethyst. Derik- 8chHfLd.Kais.Akad. 4to v Wien, 1849. 490 APPENDIX. * Harting, (P.,) Description d'un Diamant remarquable, contenant'des crystaux. Acad. roy. des Sciences. 4to. Amsterdam, 1850. Loew, Ueber den Bernstein und die Bernstein-Fauna. Berlin, 1850. Zerrenner, (Dr. Carl,) De Adamanti Dissertatio. Lipsice, 1850. Zerrenner, (C.,) Anleitung zum Diamanten. Wasclien aus Seifenge- birge, Ufer-und Flusbett-Sand. 8vo. Leipzig, 1851. Hindmarsli, (R.,) Precious Stones, being an account of the Stones mentioned in the Sacred Scriptures. 8vo. London, 1851. Booth, Encyclopedia. Philadelphia, 1852. Rose, (G.,) Das Krystallo-Chemische Mineral-system. 8vo. Leipzig, 1852. Haidinger, (W.,) Pleochroismus und Krystallstructur des Ame- thystes. Sitzungsber. der Kais. Akad. 8vo. Wien, 1854. Fontenelle, Nouveau Manuel Complet du Bijoutier. 8vo. Paris, 1855. Labarte, (M. Jules,) Handbook of the Arts of the Middle Ages and Renaissance as applied to the Decoration of Jewels, Arms, etc. 8vo. London, 1855. Schmidt, (C. J.,) Das Wichtigste iiber den Opal in Allgemeinen und iiber sein Vorkommen in Mahftsn im Besonderen. Mittheil. d. k. k. mdhr. scJiles. Gesellsch. Brunn, 1855. Volger, (G. H. O.,) Versuch einer Monographic des Borazites. Hano- ver, 1855. Volger, (G. H. 0.,) Epidot und Granat, Beobachtungen iiber das gegenseitige Verhiiltniss dieser Krystalle. 4to. Zurich, 1855. Kokscharow, (Nic. von,) Ueber die russischen Topase. 4to. Mem. de I' Acad. Imp. Petersbourg, 1856. Krause, (T. H.,) Pyrgoteles, oder die edeln Steine der Alten in Bereiche der Natur, etc. Halle, 1856. Loninser, (Gust.,) Die Marmaroscher Diamanten. 4to. Presburg, 1856. Ritter, (C.,) Der Tu-(Yu-)stein, d. i. der Tu-chi der Chinesen, Kasch der Tiirken, Yeschet der Perser, oder Jaspis der Alten, sein Fun- dort in Khotan, sein Verbrauch und Handel. 8vo. Berlin, 1856. Ginanni, (Fantuzzi M.,) Osservazioni geognostiche sul Coloramento di alcune Pietre e sulla formazione di un Agata nel Museo Ginanni di Ravenna. 8vo. 1857. Mobius, (K.,) Die echten Perlen. 4to. Hamburg, 1857. Barbot, (Ch.,) Traite complet des Pierres precieuses. 8vo. Paris, 1858. APPENDED 491 V Haidinger, (W.,) Der fiir Diamant oder noch Werthvolleree aus- gegebene Topas des Herrn Dupoisat. Sitzungsber. der Kais. Akad. 4to. Wien, 1858. Rudolph, (A.,) Die edeln Metalle und Schmucksteine, mit 37 Ta- beUen. Breslau, 1858. " Scheerer, (Th.,) Ueber den Traversellit und seine Begleiter Pyrgom, Epidot, Granat. Ein neuer Beitrag zur Beantwortung der Pluton- ischen Frage. Bericht. der Kngl. sdcJis. GeseUsch. 8vo. Leipzig, 1858. Feuchtwanger, (Dr. L.,) A Popular Treatise on Gems, in reference to their scientific value, etc. 8vo. New-York, 1859. Hessh'ug, (Th. von,) Die Perlmuschel und ihre Perlen. 8vo. Leipzig, 1859. Kluge, Edelsteinkunde. Leipzig, 1860. Pole, (W.,) Diamonds. 8vo. Land. Archaol. Trans. London, 1861. Pisani, (J.,) Sur le Grenat octoedrique de 1'Ile d'Elbe. 4to. Comptes rend, de VAcad. des Sciences. Paris, 1862. Sotto, (Js.,) Le Lapidaire du quatorzieme Siecle. 8vo. Wien, 1862. Zepharovitch, (V. v.,) Der Diamant, ein Popularer Vortrag. 8vo. Gratz, 1862. Lacaze, (Duthiers H.,) Histoire Naturelle du Corail, Organisation, Reproduction, Peche en Algerie, Industrie, etc. 8vo. Paris, 1864. Von Kobell, (Franz,) Die Mineralogie. Leipzig, 1864. Madelung, (A.,) Die Metamorphosen von Basalt und Chrysolith von Hotzendorf in Mahren. 4to. * Jahrb. d. Geol. Reichsanst. Wien, 1864. Partsch, (P.,) Catalogue of the Geological Cabinet at Vienna, with a Biographical List of the Works treating on the subjects of Ge- ology, Oryctology, and Palaeontology. 8vo. Vienna, 1864. Emanuel, (H.,) Diamonds and Precious Stones. London, 1865. Annales des Mines. Paris. Boetius, (Anselmus,) Tractatus de Lapidibus et Gemmis. Var. ed. Bondary, (Jean de la Taille de,) Blason des Pierres precieuses. Bouillon, (De la Grange,) Analysis of the Substance known by the name of Turquoise. Nick. Journ. xxi. 182. Cardanus, (Hieronymus,) De Lapidibus preciosis ; also de Subtilitate. Var. ed. Guyton-Morveau, (B. L.,) Account of certain Experiments and Infer- ences respecting the combustion of the Diamond and the Nature of its composition. Nich. Journ. iii. 298. Kohler, (H. K. A. von,) Kleine Abhandlungen zur Gemmenkunde. 492 .APPENDIX. Lucretius, De Rerum Natura. Var. ed. Mortimer, (Cromwell, M. D.,) Remarks on the Precious Stone called Turquois. Phil. Trans. Abr. viii. 324. London. Phillips, Mineralogy. Var. ed. Philostratus, De Vita Apollonii. Var. ed. Vauquelin, (Citizen,) Information respecting the earth of the Beryl. Mch.Journ.u. 393. Vauquelin, (Citizen,) Analysis of the Chrysolite of the Jewellers, proving it to be Phosphate of Lime. Nich. Journ. ii. 414. Vauquelin, (Citizen,) Analysis of the Aqua Marine or Beryl, etc. Nidi. Journ. ii. 358. Vega, (Garcilaso de la,) History of the Incas. Var. ed. Wecker, or Weckerus, Antidotae speciales de Lapidibus minus pre- tiosis alterantibus. Poggendorff's Annalen der Physik und Chemie. Brooks in the Encyclopedia Metropolitain. Berzelius' Annual Reports. London, Edinburgh and Dublin Philosophical Magazine. . Jamieson's New Edinburgh Journal of Science. Brewster's Edinburgh Journal of Science. Thomson's Records of General Science. Reports of the British Association. De Ik Beche's Report. Silliman's American Journal of Science. Haiiy, (L. Abbe,) Tableau comparatif des resultas de la Crestallo- graphie et de 1'analyse chimique, relativement a la classification des mineraux. 8vo. Figs. Paris. Kidd, (J.,) Outlines of Minerology. 2 vols. 8vo. Oxford. Karsten's Archiv fur Mineralogie. 8vo. Berlin. Glocker, Mineralogischen Jahreshefte. 8vo. Breslau. Hartmann, Jahrbuch der Mineralogie, Geologie, &c. 8vo. Leonhard und Bronn, Neues Jahrbuch fur Mineralogie, Geographie, Geologie und Petrefaktenkunde. 8vo. The British Museum, containing some Ancient Manuscripts relating to the subject : Galamazar, Liber vertutibus Lapidum Pretiosorum quern scripsit Galamazar, Thesaurarius Regis Babylonie, ipso presenti et pre- cipiente. Harleian MSS. 8vo. APPENDIX. 493 De Lapidibus, Avibus et Arboribus Indiae, Arabiae et AMcae. Har- leian M88. 8vo. Lapidum Pretiosorum usus Magicus, sive de Sigillis. Harleian MS8. 8vo. Liber Hermetis tractans de 15 Stellis et de 15 Lapidibus et de 15 Herbis et de 15 Figuris. Harleian MSS. 8vo. 494 TABLE OF THE DISTINGUISHING Name and Color. Lustre. Specific Gravity. Hardness. No. in Scale of Hard- ness. Composition. System of Crystalliza- tion. DIAMOND. Adamantine ; 8-4 to 3 -6 Scratches all 10. Pure Carbon. Monometric White, pink, yellow, red, blue, green, black, reflects prismatic other pre- cious stones. or cubical. orange, brown, opales- colors. cent. BOART. CARBONATE, (compact None. massive variety.) SAPPHIRE. d f White, blue, violet. Vitreous; very lively. 3-9 to 4-2 Scratched by diamond ; 9 Alumina, . . 9'5 Oxide of Hexagonal or rhom- o RUBY, pink, red, scratches Iron, . . 1-0 bohedral. w violet-red. all others. Lime, ... 0'5 TOPAZ, Oriental. "* j yellow. | ' AMETHYST, Orien- .g tal, purple, violet. S EMERALD, Orien- -* Jtal, green, gener- . ally pale. CHRYSOBERYL, or ORIENTAL CHRYSO- Vitreous ; sometimes 3- to 8-8 Scratched by . sapphire, 8'5 Alumina, . . 80'2 Glucina, . . 19-8 Trimetric or rhombic. LITE. Bright pale - green, greenish-yellbw, red- dish-brown. pearly. etc.; scratches quartz readily. (Trace of Per-ox- ide of Iron, of Oxide of Lead prismatic. ALEXANDRITE, when and Copper, de- exhibiting a reddish, pending on color transmittent light. CYMOPHANE, or and locality.) CHRYSOBERYL CAT'S EYE, when showing an opalescence like a cat's eye. SPINEL. Vitreous 3-8 Scratched by 8 1 Alumina, . 69'01 Monometrio Dark-red, white, blue, sapphire ; Magnesia, . 26-21 or cubical. green. scratches Protoxide PLEONASTE or CEY- quartz of Iron, . 0-71 LANITE, black. readily. Silica, . . 2-02 RUBICELLE, orange. Oxide of BALAS RUBY, rose-red. Chrome, . 1-10 TOPAZ. Vitreous. 3'5to3-6 Scratched by 8 Silica, . 34-01 Trimetric or White, greenish, yel- sapphire ; Alumina, . 58 -88 rhombic. low, orange, cinnamon, scratches Fluorine, . 15-06 bluish, pink. quartz Traces of metallic easily. oxides. 495 CHARACTERISTICS OF GEMS. Form of Crystal. Refraction. Refractive Index. Disper- sive Power. Electric Properties Fusibility. Diaphaneity. Cube, Octahedron, Rhombic dodecahedron, Tetrahedron, Hexa-octahedron. Single. White, 2-455 Brown, 2-487 0-88 Acquires posi- tive electri- city by fric- tion ; non- conductor of electricity. Infusible ; volatilized by long- continued heat. Transparent and trans- lucent ; Carbonate opaque. Hexagonal prism ; often pointed at each end. Double, in a small de- gree. 1-765 0-026 Acquires elec- tricity by friction, and retains it several hours. . * Transparent. In flat hexagonal crystals ; generally in rolled peb- bles. Double. 1-760 0-033 Acquires elec- tricity by friction, and retains it several hours. Infusible, alone. Transparent and semi- transpa- rent. Octahedron, Khombic dodecahedral octahedron, Tri-octahedron. Single. 1-755 to 1-810 0-040 .... infusible, alone. Transparent, translucent. * Eight-rhombic prism, Octahedral rhombic prism. Double, in a slight de- gree. 1-635 0-025 Acquires elec- tricity by friction and heat. Infusible. Transparent, translucent 496 TABLE OF THE DISTINGUISHING ' Name and<3olor. Lustre^. Specific Gravity. Hardness. No. in Scale of Hard- ness. Composition. System op Crystallize tion. - ] EMERALD. Vitreous. 2-67 to 2-75 Scratched by 7 '5 to 8- Silica, . . 68-50 Hexagonal Fine green. spinel ; Alumina, . 15'75 or rhom-' BERYL, or AQUAMA- scratching Glucina, -. 12'50 bohedral.^ RINE, pale sea-green, quartz, Oxide of blue, white, yellow, (specimens Iron, . . 1-00 rarely pink. vary.) Lime, . . 0'25 HYACINTH, or Vitreous, 4-07 to 4-70 Scratches 7-5 Silica, . . 33-0 Diometricoi JACINTH, brownish- (almost ad- quartz Zircon ia, . 66. S square yellow, brownish-red. amantine.) slightly. 1'eroxide of prismatic; cinnamon. Iron, . . O'l" pyramida JARGOON, various shades of green, yel- low, white, brown. GARNET. Vitreous, in- 3 5 to 4-3 Scratches 6-5 to 7 '5 Silica. . . 38-25 Monometric ALMANDINE, vio- -o let-red. clining to resinous. quartz slightly. Alumina. . 19-35 Lied Oxide or cubical o CARBUNCLE, red. of Iron, . 7 '83 o> brownish. Lime, . . 81-75 "CINNAMON- Magnesia, . 240 STONE, white, Protoxide ~" yellow, orange. | PYROPE, vermil- of Man- ganese, . 0'5U i; ion or Bohemian garnet. TOURMALINE. Green, red, brown, yel- Vitreous. 2 99 to 8 -3 Scratches quartz 7- to 7 -5 Fluorine, . 2 '28 Silica, . . 38-85 Elexagonal or rhom- low, blue, black, some- slightly. Boracic Acid, S'25 bohedral. times white. Alumina, . 81 '82 Red Oxide of Iron, . 1-27 Magnesia, . 13'89 Lime, . . 1-60 " Soda, . . . 1-28 Potash, . . 0-26 QUARTZ, -r Vitreous. 2-65 Scratches ' 7 Silica. . . 99-87 Hexagonal ROCK CRYSTAL, glass. Alumina, . or rhora- white. bohedral. AMETHYST, violet. Amethyst, . CAIRNGORM, ytllow. brown. Silica, . . 97 -5f CHRYSO PRASE, fine Alumina. . 0"25 apple-green. Red Oxide CAT'S EYE, ha vlngchu- of Iron," . 0-50 toyaxt reflection. Oxide of PLASMA, deep olive- Man- green. ganese, . 0'25 JASPER, yellow, red, green, blnck, brown. 49' CHARACTERISTICS OF GEMS. ( Continued.) Form of Crystal; Refraction. Eefractire Index. Disper- sive Power. Electric Properties. Fusibility. Diaphaneity. Hexagonal prism. Double, (very feeble.) 1-585 0-026 Acquires posi- tive electri- city by fric- Slightly fu sible be- fore the Transparent. tion. blowpipe. Long square prism, Short square pri>m. Long square octahedron. The prisms often doubly Double, in a very high degree,e- pecially in 1-990 0-044 Do. do. In fusible be- fore the blowpipe. Transparent to opaque. terminated with square the Jar- pyramids. gonn ol v_eylon. Rhombic dodecahedron. Rhombic ld uhrdral Simple. 1-159 0-088 Do. do. Fusible be fore the Transparent, opaque. cube. blowpipe. Trapezohedmn, II exa-octa hedron . )btuse rhombohedron, iexagonal prisms. Double. 1-625 0-023 Acquires posi- tive and neg- Fusible. From trans- parent to ative elec- opaque. tricitv by friction and heat. lexagonal prism, Bipvramidal, dodecahe- Doable. 1-549 0-026 Acquires posi- tive electri- Infusible. Transparent and trans- dfal. city by fric- lucent. tion. Many varie- ties, nearly opaque.) 498 TABLE OF THE DISTINGUISHING Name and Color. Lustre. Specific Gravity. Hardness. No. in Scalp of Hard- ness. Composition. System of Crystalliza- tion. BLOODSTONE, dark- green, with red spots. CAENELION, red, white, yellow. AGATE, various colors. ONYX, having black, brown and white layers. SARDONYX, hav- ing red or brownish and white layers. MOC H A-STONE,having infiltrated Oxides of Iron or Manganese, producing dendritic appearances. Vitreous. Vitreous. Vitreous, in- clining to resinous. Pearly. 8-3 to S' 14 2 -62 to 3- 2'0 to 2-3 2-5 to 2-7 Scrafchedby quartz. Scratches glass feebly. Scratches glass slightly. Various. 6- to 7' 6 5-5 to 6-5 2-5 to 3 -5 Silica, . . 39-73 Magnesia, . 60'13 Protoxide of Iron, . 9-19 Oxide of Nickel, . 0-32 Oxide of Man- ganese, . 0'09 Alumina, . 0'22 Phos. Acid, . 27-84 Alumina, . 47*45 Oxide of Copper, . 2-05 Oxide of Iron, . .'1-10 Oxide of Man- ganese, . 0'50 Phosphate of Lime, . 3'41 Water, . . 18-18 Silica, . . 91-32 Water, . . 8-63 Traces of mineral coloring-matter Carbonate o: Lime, organic matter. Tri metric or rhombic. None. None. None. CHRYSOLITE. PERIDOT, olive-green. OLIVINE. TURQUOISE. Blue, green, white. OPAL. Colorless, red, white, green, gray, black, yel- low. (Iridescent.) PEARL. White, yellow, pink, black, violet, brown, gray. 499 CHARACTERISTICS OF GEMS. ( Continued.) Form of Crystal. Refraction. Refractive Index. Disper- sive Power. Electric Properties. Fusibility. Diaphaneity. Generally in rolled grains and pebbles. Double. 1-660 1-088 Acquires elec- tricity by friction. Infusible. Transparent and trans- lucent None. .... .... .... None. Infusible. Opaque. Translucent at edges. None. .... .... ,-'>r?P> Infusible. Semi-trans- parent. None. None. None. None. None. Calcines by moderate* heat. Opaque ; sometimes semi-trans- parent. 502 APPENDIX. The value of stones above five carats is not attempted to be given, as it is impossible to fix it with any accuracy. It depends entirely on the demand for any particular size and the supply in the market ; it remains a matter of negotiation between the buyer and seller. When a Diamond has a very decided color, such as blue, red, green, &c., it is called a fancy stone, and will bring a most exorbitant price. A stone of five grains, of a brilliant emerald-green color, for which, if white, not more than 28 stg. could be obtained, has been known to sell for 320 stg. The terms first water, second water, &c., mean only first and second quality. Diamonds, when perfect, should be clear as a drop of the purest water, and they are described as second or third water when more or less clear, until decidedly yel- low or brown, when they are termed colored. The value of stones of the first quality of a less weight than two grains, (half a carat,) is, according to Mr. Emanuel, 10 stg. per carat ; the second quality, 8 stg. ; the third, 7 stg. per carat. The plates representing the sizes of the Diamonds, given in this Treatise, are drawn from nature ; still it is quite difficult to get at the actual weight, for the Diamond cutters of the present day turn their attention more to the production of the greatest weight from a given quantity of rough Diamond, than to the production of per- fectly proportioned stones, for which reason we often meet with stones weighing three carats, whose proper weight, if reasonably spread, should be two, which renders them less valuable and not nearly so brilliant as one of two carats properly cut ; any over or under weight only detracts from its beauty. A well proportioned spread Diamond finds more amateurs than a heavy one. At present the following prices may be quoted for Diamonds in gold currency, *2 grains, (half a carat,) from ......... $68 to $75, gold. 1 carat, " ... 110 to 140 " 1-J- " (6 grains ) " . 200 the stone " 2 " (8 " ) " . .. 400 3 " (12 " "> " . . . 1 200 to 1 400 " 4 " (16 " ) " . 1 600 to 2 000 " 6 " (20 " ) " . 3 000 to 4 000 " * 4 grains are equal to 1 carat. 151)6 carats " "1 ounce troy weight. APPENDIX. 503 Mr. Emanuel's price list quotes for 1865, in pounds sterling and shillings : A Brilliant, weighing i of a carat, stg. 5 10*. 5d. f " " " 9 10 " " 1 " "...." 18 " " li " " " 28 ft -Jl (( ft gg **< " If " " " 48 ' ~ \ -'. 2 " " 65 ^-: w- 2i \- : -* ".,':..;*;' 70 *"'''-"' " 2 " " " 88 V-.--< ..,"/' 2f " "...." 100 > 3 " "...." 125 3i " " .... 135 3i " " ...'. " 150 3f " "...." 175 '.'"*'. 4 "".;>; * w 220 4J " " " 230 4i " " " 250 4| " "...." 280 5 " "...." 320 The Rose Diamond, which is not much in use in Europe, but more in South America, has not a very fixed value. The small Rose Dia- monds, if under 40 to the carat, are worth about five shillings each ; above that size, and up to one carat, bring from 9 stg. to 11 stg. the carat. Ruby and Emerald. Both these gems, when really fine, free from any defect, in color or size, are worth as much as Diamonds of the same weight. ^ A fair Ruby is worth from $30 to $40 per carat. A fine and pure Ruby, well spread and proportioned, is worth, according to Mr. Emanuel Of 1 carat, stg. 14 to 20 H " " 25 to 35 2 " " 70 to 80 3 " " 200 to 250 4 " " 400to450 And those below the weight of one carat range from 2 to 8 stg. per carat ; while stones of greater weight than four carats are of 504 APPENDIX. Bucli exceptional occurrence as to command fancy prices. Again, a Ruby of four carats, but of a pale color, may not be worth 12 stg. The Emerald is so rarely found perfect that the saying, "An Emerald without a flaw," has passed into a proverb. A good Em- erald is at the present day worth more than a Ruby, on account of the pleasing effect it has both by day and candle-light, and is a very favorite gem ; stands high in value ; but the Emeralds found lat- terly and brought into market are far inferior to those formerly found. A good Emerald is worth in this country $40 to $50 per carat. In England the price ranges from 5s. to 15 stg. per carat ; but one of deep, rich grass-green color, clear and free from flaws, may bring from 20 to 40 stg. per carat. Sapphire. A fine, perfect, evenly colored spread Sapphire, weigh- ing one carat, of a deep rich blue color, by night as well as by day, is worth 20 stg. ; it does not, however, increase so much in isalue in proportion to its size. The Spinel or Balajs-Ruby, if of good quality, is sold from 10s. to 8 stg. per carat. The value is extremely uncertain and variable ; it depends entirely on caprice and fashion. The Topaz. The commercial nature of the Topaz as a jewel is entirely fictitious. A very fine stone can now be bought for a few shillings sterling, whilq it would have brought a great deal more when in fashion. Pink Topaz brings from 2 stg. to 20 stg. per ounce, the price depending on the depth of the pink color. Beryl or Aquamarine. The commercial value of this stone is trifling, and is used mostly for imitation jewelry. Zircon, Hyacinth or Jacinth, are also called Jar goon. These stones, are identically the same, but differ in color ; the red varieties are sometimes sold for inferior Rubies. The Jargoon is frequently cut in the form of a Rose Diamond, which is flat at the bottom and pointed at the top. The price is purely%rbitrary. The Garnet, Essonite, Pyrope and Almandine. The color of the Syrian Garnet, being of deep crimson, is at present much in vogue, and commands a fair price, say from $1 to $2 per carat. The Bohemian Garnets are worth from $15 to $25 per ounce. Amethyst. A fine deep-colored stone, of the size of a twenty-five cent piece, is worth from $80 to $100 per ounce ; smaller sizes and inferior qualities are sold for 50 cents to $10 apiece. Peridote, Chrysolite. The value of both stones is but small ; fair specimens of good size may be bought at from 25c. to $5 per carat. Turquoise. The Persian is much used in jewelry ; small, clear APPENDIX. 505 stones bring from sixpence to 20*. stg. each, while a fine Ring stone will realize from 10 stg. to 40 stg. Large Turquoise, of good quality and fine color, are extremely rare, and realize extrava- gant prices. Opal. The value of the precious Opal depends entirely on the brilliancy and play of its colors ; large, fine gems, of extraordinary beauty, have brought fabulous prices. They are not sold by the carat, but by the piece. Coral. The red Coral, which formerly was the most valuable, is now worth far less than the color which was formerly worthless. The pale, delicate pink, similar to that of the inside of the pale rose leaf, is sought after, but very scarce ; a Coral of this tint is very valuable. 48 stg. per ounce has lately been paid in London. A large bead or drop will readily realize from 30 stg. to 40 stg. ; small pieces, however, may be had for $4 to $6 per ounce. Pearls. The value for perfectly pure round Pearls, of a smooth and lustrous skin, perfectly free from specks or discoloration of any sort, of small size, is from $1 to $2 a grain. 4 grain Pearls, 2 to 3 " 6 " " 5 to 6 10 " " 8 to 10 The following is Mr. Emanuel's table of prices of Pearls, viz. : A Pearl of 1 grain is worth from 2*. to 2*. Qd. " 2 " " " 6s. Qd. to 7. Qd. 3 " " " 12*. to 16*. 4 " " " 22*. to 28*. 5 " " " 35*. to 48*. 6 " " " 55*. to 65*. 8 " " " 90*. to 110*. 10 " " " 8 stg. to 9 stg. " 12 " " " 12 " to 15 " " 14 " " 15 " to 18 " 16 " " " 20 " to 30 " 18 " " " 30 " to 40 " 20 " " " 40 " to 50 " 24 " " 60 " to 70 " 30 " " " 80 " to 100 " Round Pearls above the latter weight are of such rare occurrence and command such exceptional prices, that it would be useless to attempt any scale of valuation. 14 DAY USE RETU RROWED RN TQJ)ESK ERO]VOWai] LOAN IDE.?!. This book is due on the last date stamped below, or on the date to which renewed. Renewed books are subject to immediate recall. 22Jun'fiOFW JUN4 1957 T R . - REC'D LD JUN 8 19fin MAY 9 1957 IfiHl w ** IOv /9l y 3Sep'58CSf <^Cl 6//f g _ " - "wyasr- saM: 22Ja" REC'D T ? LD 21-100m-6,'56 (B9311slO)476 University of California Berkeley YB ,'5203